Re: guix import error + New: setting up a jupyterlab environment

[Efraim Flashner <efraim@flashner.co.il>]

It looks like you need to add python-ipykernel to native-inputs. Unless it's needed to run the program and not just for the test suite, in which case it should go in propagated-inputs. There's no network available in the build environment so it can't retrieve ipykernel while building.


On October 19, 2020 2:31:53 PM UTC, Zelphir Kaltstahl <zelphirkaltstahl@posteo.de> wrote:
>Hello Efraim!
>
>Thank you! Your idea of replacing "-" with "_" seems to partially help:
>
>The package is downloaded and byte compiled. However, afterwards there
>is a problem, when it tries to copy the byte-compiled files in the "wrap
>phase" (comments inserted in some places):
>
>~~~~START~~~~
>### ... a lot of output before this ...
>
>byte-compiling /gnu/store/yr7q21bws1xgx3p2dy9cfdiknjpsajm6-python-jupyterlab-server-1.2.0/lib/python3.8/site-packages/jupyterlab_server/__init__.py to __init__.cpython-38.pyc
>byte-compiling /gnu/store/yr7q21bws1xgx3p2dy9cfdiknjpsajm6-python-jupyterlab-server-1.2.0/lib/python3.8/site-packages/jupyterlab_server/_version.py to _version.cpython-38.pyc
>byte-compiling /gnu/store/yr7q21bws1xgx3p2dy9cfdiknjpsajm6-python-jupyterlab-server-1.2.0/lib/python3.8/site-packages/jupyterlab_server/app.py to app.cpython-38.pyc
>byte-compiling /gnu/store/yr7q21bws1xgx3p2dy9cfdiknjpsajm6-python-jupyterlab-server-1.2.0/lib/python3.8/site-packages/jupyterlab_server/handlers.py to handlers.cpython-38.pyc
>byte-compiling /gnu/store/yr7q21bws1xgx3p2dy9cfdiknjpsajm6-python-jupyterlab-server-1.2.0/lib/python3.8/site-packages/jupyterlab_server/listings_handler.py to listings_handler.cpython-38.pyc
>byte-compiling /gnu/store/yr7q21bws1xgx3p2dy9cfdiknjpsajm6-python-jupyterlab-server-1.2.0/lib/python3.8/site-packages/jupyterlab_server/process.py to process.cpython-38.pyc
>byte-compiling /gnu/store/yr7q21bws1xgx3p2dy9cfdiknjpsajm6-python-jupyterlab-server-1.2.0/lib/python3.8/site-packages/jupyterlab_server/process_app.py to process_app.cpython-38.pyc
>byte-compiling /gnu/store/yr7q21bws1xgx3p2dy9cfdiknjpsajm6-python-jupyterlab-server-1.2.0/lib/python3.8/site-packages/jupyterlab_server/server.py to server.cpython-38.pyc
>byte-compiling /gnu/store/yr7q21bws1xgx3p2dy9cfdiknjpsajm6-python-jupyterlab-server-1.2.0/lib/python3.8/site-packages/jupyterlab_server/servertest.py to servertest.cpython-38.pyc
>byte-compiling /gnu/store/yr7q21bws1xgx3p2dy9cfdiknjpsajm6-python-jupyterlab-server-1.2.0/lib/python3.8/site-packages/jupyterlab_server/settings_handler.py to settings_handler.cpython-38.pyc
>byte-compiling /gnu/store/yr7q21bws1xgx3p2dy9cfdiknjpsajm6-python-jupyterlab-server-1.2.0/lib/python3.8/site-packages/jupyterlab_server/themes_handler.py to themes_handler.cpython-38.pyc
>byte-compiling /gnu/store/yr7q21bws1xgx3p2dy9cfdiknjpsajm6-python-jupyterlab-server-1.2.0/lib/python3.8/site-packages/jupyterlab_server/workspaces_handler.py to workspaces_handler.cpython-38.pyc
>byte-compiling /gnu/store/yr7q21bws1xgx3p2dy9cfdiknjpsajm6-python-jupyterlab-server-1.2.0/lib/python3.8/site-packages/jupyterlab_server/tests/__init__.py to __init__.cpython-38.pyc
>byte-compiling /gnu/store/yr7q21bws1xgx3p2dy9cfdiknjpsajm6-python-jupyterlab-server-1.2.0/lib/python3.8/site-packages/jupyterlab_server/tests/test_settings_api.py to test_settings_api.cpython-38.pyc
>byte-compiling /gnu/store/yr7q21bws1xgx3p2dy9cfdiknjpsajm6-python-jupyterlab-server-1.2.0/lib/python3.8/site-packages/jupyterlab_server/tests/test_workspaces_api.py to test_workspaces_api.cpython-38.pyc
>byte-compiling /gnu/store/yr7q21bws1xgx3p2dy9cfdiknjpsajm6-python-jupyterlab-server-1.2.0/lib/python3.8/site-packages/jupyterlab_server/tests/utils.py to utils.cpython-38.pyc
>
>### ... seems byte-compiling went without problems, but not comes the problem ...
>
>running install_egg_info
>Copying jupyterlab_server.egg-info to /gnu/store/yr7q21bws1xgx3p2dy9cfdiknjpsajm6-python-jupyterlab-server-1.2.0/lib/python3.8/site-packages/jupyterlab_server-1.2.0-py3.8.egg-info
>running install_scripts
>phase `install' succeeded after 0.3 seconds
>starting phase `wrap'
>find-files: /gnu/store/yr7q21bws1xgx3p2dy9cfdiknjpsajm6-python-jupyterlab-server-1.2.0/bin: No such file or directory
>find-files: /gnu/store/yr7q21bws1xgx3p2dy9cfdiknjpsajm6-python-jupyterlab-server-1.2.0/sbin: No such file or directory
>phase `wrap' succeeded after 0.0 seconds
>starting phase `check'
>running "python setup.py" with command "test" and parameters ()
>running test
>Searching for ipykernel
>Reading https://pypi.org/simple/ipykernel/
>Download error on https://pypi.org/simple/ipykernel/: [Errno -2] Name or service not known -- Some packages may not be found!
>Couldn't find index page for 'ipykernel' (maybe misspelled?)
>Scanning index of all packages (this may take a while)
>Reading https://pypi.org/simple/
>Download error on https://pypi.org/simple/: [Errno -2] Name or service not known -- Some packages may not be found!
>No local packages or working download links found for ipykernel
>error: Could not find suitable distribution for Requirement.parse('ipykernel')
>command "python" "-c" "import setuptools, tokenize;__file__='setup.py';f=getattr(tokenize, 'open', open)(__file__);code=f.read().replace('\\r\\n', '\\n');f.close();exec(compile(code, __file__, 'exec'))" "test" failed with status 1
>~~~~~END~~~~~
>
>So it seems, that while the download URL is corrected, there is another
>place, where Guix has an error now, resulting in a final error shown in
>command line:
>
>~~~~START~~~~
>$ guix time-machine --channels=channels.scm -- environment --manifest=manifest.scm --load=jupyterlab.scm
>Updating channel 'guix' from Git repository at 'https://git.savannah.gnu.org/git/guix.git'...
>substitute: updating substitutes from 'https://ci.guix.gnu.org'... 100.0%
>The following derivations will be built:
>   /gnu/store/wzmfn9m45bmsbrx094rv3lf3w0rpmw49-python-pytest-check-links-0.3.0.drv
>   /gnu/store/96xf5mrg134mcsp01b0m1qs1lxkb401a-python-jupyterlab-server-1.2.0.drv
>   /gnu/store/32a28hd7aainwn0hfsnf3blh8prmfz61-jupyterlab_server-1.2.0.tar.gz.drv
>
>3,9 MB will be downloaded
>downloading from https://ci.guix.gnu.org/nar/lzip/54kpl9psx16jwic4gpnjwh44kim04wlk-python-notebook-5.7.4 ...
> python-notebook-5.7.4  3.7MiB                                                                                                                                                                                                        5.1MiB/s 00:01 [##################] 100.0%
>
>building /gnu/store/32a28hd7aainwn0hfsnf3blh8prmfz61-jupyterlab_server-1.2.0.tar.gz.drv...
>downloading from https://files.pythonhosted.org/packages/source/j/jupyterlab_server/jupyterlab_server-1.2.0.tar.gz ...
>building /gnu/store/wzmfn9m45bmsbrx094rv3lf3w0rpmw49-python-pytest-check-links-0.3.0.drv...
>building /gnu/store/96xf5mrg134mcsp01b0m1qs1lxkb401a-python-jupyterlab-server-1.2.0.drv...
>\ 'check' phasebuilder for `/gnu/store/96xf5mrg134mcsp01b0m1qs1lxkb401a-python-jupyterlab-server-1.2.0.drv' failed with exit code 1
>build of /gnu/store/96xf5mrg134mcsp01b0m1qs1lxkb401a-python-jupyterlab-server-1.2.0.drv failed
>View build log at '/var/log/guix/drvs/96/xf5mrg134mcsp01b0m1qs1lxkb401a-python-jupyterlab-server-1.2.0.drv.bz2'.
>guix environment: error: build of `/gnu/store/96xf5mrg134mcsp01b0m1qs1lxkb401a-python-jupyterlab-server-1.2.0.drv' failed
>~~~~~END~~~~~
>
>Apparently ipykernel is not found, but when I visit
>https://pypi.org/simple/ipykernel/, I see packages there.
>
>From the logs:
>
>~~~~START~~~~
>Download error on https://pypi.org/simple/ipykernel/: [Errno -2] Name or service not known -- Some packages may not be found!
>Couldn't find index page for 'ipykernel' (maybe misspelled?)
>~~~~~END~~~~~
>
>Do I need to add another input in my `jupyterlab.scm`? (How?) Or perhaps
>I need to create a separate `ipykernel.scm` which contains the output of
>`guix import pypi --recursive ipykernel`?
>
>However, it somehow seems to fail for PyPI simple in general (from the
>logs again):
>
>~~~~START~~~~
>Reading https://pypi.org/simple/
>Download error on https://pypi.org/simple/: [Errno -2] Name or service not known -- Some packages may not be found!
>No local packages or working download links found for ipykernel
>error: Could not find suitable distribution for Requirement.parse('ipykernel')
>command "python" "-c" "import setuptools, tokenize;__file__='setup.py';f=getattr(tokenize, 'open', open)(__file__);code=f.read().replace('\\r\\n', '\\n');f.close();exec(compile(code, __file__, 'exec'))" "test" failed with status 1
>~~~~~END~~~~~
>
>Thanks,
>Zelphir
>
>
>On 10/18/20 6:35 PM, Efraim Flashner wrote:
>> On Sun, Oct 18, 2020 at 01:55:49PM +0200, Zelphir Kaltstahl wrote:
>>> Hello Guix Users, hello Zimoun and Tobias!
>>>
>>> Thanks for your information regarding the importer syntax thing.
>>>
>>> I continued trying to get a jupyterlab environment today.
>>>
>>> Here is what I did so far:
>>>
>>> (1) Create my manifest file:
>>>
>>> ~~~~START~~~~
>>> (specifications->manifest
>>>  '("python"))
>>> ~~~~~END~~~~~
>>>
>>> (2) Create my channels file:
>>>
>>> ~~~~START~~~~
>>> $ guix describe --format=channels > channels.scm
>>> $ cat channels.scm
>>> (list (channel
>>>         (name 'guix)
>>>         (url "https://git.savannah.gnu.org/git/guix.git")
>>>         (commit
>>>           "6ca673b30dac281ba27a8dac242c0ac83e5e354b")
>>>         (introduction
>>>           (make-channel-introduction
>>>             "9edb3f66fd807b096b48283debdcddccfea34bad"
>>>             (openpgp-fingerprint
>>>               "BBB0 2DDF 2CEA F6A8 0D1D  E643 A2A0 6DF2 A33A 54FA")))))
>>> ~~~~~END~~~~~
>>>
>>> (3) Create my jupyterlab PyPI import file, this time around using the
>>> "/" instead of "@" for specifying the version:
>>>
>>> ~~~~START~~~~
>>> $ guix import pypi --recursive jupyterlab/2.1.5 > jupyterlab.scm
>>> ~~~~~END~~~~~
>>>
>>> (4) Add missing import expressions and add output expression at the end:
>>>
>>> ~~~~START~~~~
>>> ;; add module imports
>>> (use-modules
>>>  (guix packages)
>>>  (guix download)
>>>  (guix build-system python)
>>>  ((guix licenses) #:prefix license:)
>>>  ;; use `guix environment --ad-hoc python-jinja2 -- guix package -A python-jinja2` to find the location of python-jinja2, which is gnu/packages/python-xyz.scm
>> This can be just 'guix package -A python-jinja2', no need for the
>> environment.
>>
>>>  (gnu packages python-xyz)
>>>  ;; for python-tornado
>>>  (gnu packages python-web)
>>>  ;; for python-pytest
>>>  (gnu packages check))
>>>
>>> ;; QUESTION: Why are those required packages not imported by guix automatically?
>>> ;; QUESTION: Why are the manually imported packages not actually in files with their own name, but instead jinja2 -> python-xyz, tornado -> python-web, and pytest -> check?
>>> ;; QUESTION: Is my process of finding the files in which the packages are correct or just working by chance?
>>>
>>> (define-public python-jupyterlab-server
>>>   (package
>>>     (name "python-jupyterlab-server")
>>>     (version "1.2.0")
>>>     (source
>>>       (origin
>>>         (method url-fetch)
>>>         (uri (pypi-uri "jupyterlab-server" version))
>>>         (sha256
>>>           (base32
>>>             "132xby7531rbrjg9bqvsx86birr1blynjxy8gi5kcnb6x7fxjcal"))))
>>>     (build-system python-build-system)
>>>     (propagated-inputs
>>>       `(("python-jinja2" ,python-jinja2)
>>>         ("python-json5" ,python-json5)
>>>         ("python-jsonschema" ,python-jsonschema)
>>>         ("python-notebook" ,python-notebook)
>>>         ("python-requests" ,python-requests)))
>>>     (native-inputs
>>>       `(("python-pytest" ,python-pytest)
>>>         ("python-requests" ,python-requests)))
>>>     (home-page "https://jupyter.org")
>>>     (synopsis "JupyterLab Server")
>>>     (description "JupyterLab Server")
>>>     (license license:bsd-3)))
>>>
>>> (define-public python-jupyterlab
>>>   (package
>>>     (name "python-jupyterlab")
>>>     (version "2.1.5")
>>>     (source
>>>       (origin
>>>         (method url-fetch)
>>>         (uri (pypi-uri "jupyterlab" version))
>>>         (sha256
>>>           (base32
>>>             "162jn51cg36fsn4l2zhnb5n4nbkhm9wlv974ggcnmdij3i4r4yya"))))
>>>     (build-system python-build-system)
>>>     (propagated-inputs
>>>       `(("python-jinja2" ,python-jinja2)
>>>         ("python-jupyterlab-server"
>>>          ,python-jupyterlab-server)
>>>         ("python-notebook" ,python-notebook)
>>>         ("python-tornado" ,python-tornado)))
>>>     (native-inputs
>>>       `(("python-pytest" ,python-pytest)
>>>         ("python-pytest-check-links"
>>>          ,python-pytest-check-links)
>>>         ("python-requests" ,python-requests)
>>>         ("python-virtualenv" ,python-virtualenv)
>>>         ("python-wheel" ,python-wheel)))
>>>     (home-page "http://jupyter.org")
>>>     (synopsis
>>>       "The JupyterLab notebook server extension.")
>>>     (description
>>>       "The JupyterLab notebook server extension.")
>>>     (license license:bsd-3)))
>>>
>>> python-jupyterlab
>>> ~~~~~END~~~~~
>>>
>>> And as noted in the comments, I have 3 questions at this point:
>>>
>>> (Q1) Why are those required packages not imported by guix automatically?
>>> (My guess: This functionality simply has not yet been implemented.)
>>>
>>> (Q2) Why are the manually imported packages not actually in files with
>>> their own name, but instead jinja2 -> python-xyt, tornado -> python-web,
>>> and pytest -> check? Why not (gnu packages python pytest) for example?
>>>
>>> (Q3) Is my process of finding the files in which the packages are
>>> correct or just working by chance? Basically I am creating temporary
>>> environments, in which I then lookup "where would the package be
>>> installed" and then exit the temporary environment to use that
>>> information in my imported package file's import expressions /
>>> use-modules expression. This seems to be a bit of a convoluted process,
>>> though worth it, if it always works in the end.
>>>
>>> (4) Now I run my time-machine command:
>>>
>>> ~~~~START~~~~
>>> $ guix time-machine --channels=channels.scm -- environment --manifest=manifest.scm --load=jupyterlab.scm
>>> ~~~~~END~~~~~
>>>
>>> This take a moment and then I get an error (the full output is longer,
>>> but when running it multiple times, already successful steps are not all
>>> done repeatedly, so the output is then reduced to what fails):
>>>
>>> ~~~~START~~~~
>>> $ guix time-machine --channels=channels.scm -- environment --manifest=manifest.scm --load=jupyterlab.scm
>>> Updating channel 'guix' from Git repository at 'https://git.savannah.gnu.org/git/guix.git'...
>>> The following derivations will be built:
>>>    /gnu/store/wzmfn9m45bmsbrx094rv3lf3w0rpmw49-python-pytest-check-links-0.3.0.drv
>>>    /gnu/store/n9i421lrbwrr8d0947w5vma7rhy3iyba-python-jupyterlab-server-1.2.0.drv
>>>    /gnu/store/s7jc2dbb0bnrahxklmszmpfv8klgw3sd-jupyterlab-server-1.2.0.tar.gz.drv
>>>
>>> 4,2 MB will be downloaded
>>> downloading from https://ci.guix.gnu.org/nar/lzip/2nahbs5v8q073gjmy224gk0h5lsh1kkw-python-nbconvert-5.0.0b1 ...
>>>  python-nbconvert-5.0.0b1  301KiB                                                                                                                                                                                                     2.0MiB/s 00:00 [##################] 100.0%
>>>
>>> building /gnu/store/s7jc2dbb0bnrahxklmszmpfv8klgw3sd-jupyterlab-server-1.2.0.tar.gz.drv...
>>> |builder for `/gnu/store/s7jc2dbb0bnrahxklmszmpfv8klgw3sd-jupyterlab-server-1.2.0.tar.gz.drv' failed to produce output path `/gnu/store/92md7gh966n4fzj6al267lqq4xjx0ncf-jupyterlab-server-1.2.0.tar.gz'
>>> build of /gnu/store/s7jc2dbb0bnrahxklmszmpfv8klgw3sd-jupyterlab-server-1.2.0.tar.gz.drv failed
>>> View build log at '/var/log/guix/drvs/s7/jc2dbb0bnrahxklmszmpfv8klgw3sd-jupyterlab-server-1.2.0.tar.gz.drv.bz2'.
>>> cannot build derivation `/gnu/store/n9i421lrbwrr8d0947w5vma7rhy3iyba-python-jupyterlab-server-1.2.0.drv': 1 dependencies couldn't be built
>>> killing process 7384
>>> guix environment: error: build of `/gnu/store/n9i421lrbwrr8d0947w5vma7rhy3iyba-python-jupyterlab-server-1.2.0.drv' failed
>>> ~~~~~END~~~~~
>>>
>>> OK, an error, perhaps I can understand it. Lets look at that log file:
>>>
>>> ~~~~START~~~~
>>> $ cp /var/log/guix/drvs/s7/jc2dbb0bnrahxklmszmpfv8klgw3sd-jupyterlab-server-1.2.0.tar.gz.drv.bz2 .
>>> $ bzip2 --decompress jc2dbb0bnrahxklmszmpfv8klgw3sd-jupyterlab-server-1.2.0.tar.gz.drv.bz2
>>> $ cat jc2dbb0bnrahxklmszmpfv8klgw3sd-jupyterlab-server-1.2.0.tar.gz.drv
>>>
>>> Starting download of /gnu/store/92md7gh966n4fzj6al267lqq4xjx0ncf-jupyterlab-server-1.2.0.tar.gz
>>> From https://files.pythonhosted.org/packages/source/j/jupyterlab-server/jupyterlab-server-1.2.0.tar.gz...
>>> download failed "https://files.pythonhosted.org/packages/source/j/jupyterlab-server/jupyterlab-server-1.2.0.tar.gz" 404 "Not Found"
>>>
>>> Starting download of /gnu/store/92md7gh966n4fzj6al267lqq4xjx0ncf-jupyterlab-server-1.2.0.tar.gz
>>> From https://ci.guix.gnu.org/file/jupyterlab-server-1.2.0.tar.gz/sha256/132xby7531rbrjg9bqvsx86birr1blynjxy8gi5kcnb6x7fxjcal...
>>> download failed "https://ci.guix.gnu.org/file/jupyterlab-server-1.2.0.tar.gz/sha256/132xby7531rbrjg9bqvsx86birr1blynjxy8gi5kcnb6x7fxjcal" 404 "Not Found"
>>>
>>> Starting download of /gnu/store/92md7gh966n4fzj6al267lqq4xjx0ncf-jupyterlab-server-1.2.0.tar.gz
>>> From https://tarballs.nixos.org/sha256/132xby7531rbrjg9bqvsx86birr1blynjxy8gi5kcnb6x7fxjcal...
>>> download failed "https://tarballs.nixos.org/sha256/132xby7531rbrjg9bqvsx86birr1blynjxy8gi5kcnb6x7fxjcal" 404 "Not Found"
>>>
>>> Starting download of /gnu/store/92md7gh966n4fzj6al267lqq4xjx0ncf-jupyterlab-server-1.2.0.tar.gz
>>> From https://archive.softwareheritage.org/api/1/content/sha256:5431d9dde96659364b7cc877693d5d21e7b80cea7ae3959ecc2b87518e5f5d8c/raw/...
>>> download failed "https://archive.softwareheritage.org/api/1/content/sha256:5431d9dde96659364b7cc877693d5d21e7b80cea7ae3959ecc2b87518e5f5d8c/raw/" 404 "Not Found"
>>> failed to download "/gnu/store/92md7gh966n4fzj6al267lqq4xjx0ncf-jupyterlab-server-1.2.0.tar.gz" from "https://files.pythonhosted.org/packages/source/j/jupyterlab-server/jupyterlab-server-1.2.0.tar.gz"
>>> ~~~~~END~~~~~
>>>
>>> So it seems, that the jupyterlab-server file is simply not downloadable
>>> any longer!
>>>
>>> Trying using wget:
>>>
>>> ~~~~START~~~~
>>> $ wget https://files.pythonhosted.org/packages/source/j/jupyterlab-server/jupyterlab-server-1.2.0.tar.gz
>>> --2020-10-18 13:49:52--  https://files.pythonhosted.org/packages/source/j/jupyterlab-server/jupyterlab-server-1.2.0.tar.gz
>>> Resolving files.pythonhosted.org (files.pythonhosted.org)... 2a04:4e42:9::319, 151.101.37.63
>>> Connecting to files.pythonhosted.org (files.pythonhosted.org)|2a04:4e42:9::319|:443... failed: Connection refused.
>>> Connecting to files.pythonhosted.org (files.pythonhosted.org)|151.101.37.63|:443... connected.
>>> HTTP request sent, awaiting response... 404 Not Found
>>> 2020-10-18 13:49:53 ERROR 404: Not Found.
>>> ~~~~~END~~~~~
>>>
>>> So now I am out of ideas. It seems the file is not available any longer
>>> and the definition of jupyterlab needs to be updated somewhere, so that
>>> it does not try to download an old or non-existent version of
>>> jupyter-labserver. But how is this usually done? Can I specify it
>>> somewhere in one of the 3 files I have, or am I dependent on someone
>>> fixing the jupyterlab-server dependency / input for juypterlab?
>>>
>>> Thanks for your help so far! Tell me, if I need to provide any more
>>> information to solve the problem.
>> Try chaning the URL line to (uri (pypi-uri "jupyterlab_server" version)),
>> with an underscore (_). I don't have any special suggestions for knowing
>> that it should be an underscore instead of a dash. The best I have is
>> the output from 'guix import pypi jupyterlab-server:
>>
>> (ins)efraim@E5400 ~$ guix import pypi jupyterlab-server
>>
>> Starting download of /tmp/guix-file.ayJ41F
>> From https://files.pythonhosted.org/packages/92/54/5f321ca4cebfb644ac59eb21601b46a2ff9831ffe1b4e5a588f2a7e98d48/jupyterlab_server-1.2.0.tar.gz...
>>  …er-1.2.0.tar.gz  22KiB               57KiB/s 00:00 [##################] 100.0%
>>
>>
>>
>>> Best regards,
>>> Zelphir
>>>
>>>
>>> On 10/16/20 2:25 PM, Tobias Geerinckx-Rice wrote:
>>>> Zelphir,
>>>>
>>>> Zelphir Kaltstahl 写道：
>>>>> $ guix import pypi 'jupyterlab@2.1.5' --recursive
>>>> It will work if you substitute ‘/’ for ‘@’.  Yes, this is a happy
>>>> accident specific to the PyPI importer, and I'm sure you can guess why
>>>> it happens to work.
>>>>
>>>>>> guix import hackage mtl@2.1.3.1
>>>>> But that is in the "hackage" import section. Is the same not available
>>>>> for PyPI?
>>>> [...]
>>>>
>>>>> Do the various importers work differently?
>>>> Unfortunately so.  It would be great(TM) if PACKAGE[@VERSION] were
>>>> standard.  Each importer could handle it properly (e.g., by turning it
>>>> into "/") or return a friendlier ‘the foo importer does not yet
>>>> support versions’ error.
>>>>
>>>> I don't have the time, but this sounds like a good intermediate-level
>>>> hack for someone who does :-)
>>>>
>>>> Kind regards,
>>>>
>>>> T G-R
>>> -- 
>>> repositories: https://notabug.org/ZelphirKaltstahl
>>>
>-- 
>repositories: https://notabug.org/ZelphirKaltstahl
>

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