WIP gnu: poetry: Update to 1.0.3.

[Tanguy Le Carrour <tanguy@bioneland.org>]

Dear Guix,

I'm working on updating Poetry to version 1.0.3 and I have a problem
with the version of a dependency.

Poetry now depends on python-keyring >=20.0.0,<21.0.0. In Guix we
have python-keyring	21.0.0, so it does not work once installed!

What am I supposed to do?

I see 3 different ways out of this:
- patch the package to make it use our version (I tried but failed [1]);
- ask upstream to update dependencies;
- declare a new package python-keyring-20.0.0 and use it as an input.

[1]: attempt to patch setup.py
-    (arguments `(#:tests? #f))                    ; tests depend on dbus service
+    (arguments
+     `(#:tests? #f ;; Pypi does not have tests.
+       #:phases
+       (modify-phases %standard-phases
+         (add-after 'unpack 'change-dependencies
+           (lambda _
+             ;; Guix has version 21.0.0 of python-keyring
+             (invoke "sed" "-i" "-e"
+                     "s/keyring>=20.0.1,<21.0.0/keyring>=20.0.1,<22.0.0/"
+                     "setup.py")
+             #t)))))

Any help welcome!

-- 
Tanguy