It looks like module tkinter doesn't load for some reason.  Here is the
tail of the build log:

starting phase `sanity-check'
validating 'future'
/gnu/store/9qknps8svnw5njfr823bm1il1gw5nxlm-python2-future-0.18.2/lib/python2.7/site-packages
...checking requirements: OK
...trying to load module _dummy_thread: OK
...trying to load module _markupbase: OK
...trying to load module _thread: OK
...trying to load module builtins: OK
...trying to load module copyreg: OK
...trying to load module future: OK
...trying to load module html: OK
...trying to load module http: OK
...trying to load module libfuturize: OK
...trying to load module libpasteurize: OK
...trying to load module past: OK
...trying to load module queue: OK
...trying to load module reprlib: OK
...trying to load module socketserver: OK
...trying to load module tkinter: ERROR:
Traceback (most recent call last):
  File "/gnu/store/nwwr89v2vyg1hs48i49m083vhczsgh3m-sanity-check.py", line
69, in <module>
    importlib.import_module(name)
  File
"/gnu/store/y14nmmzzcs2a6m2gnn2diak2gkf5v2av-python2-2.7.18/lib/python2.7/importlib/__init__.py",
line 37, in import_module
    __import__(name)
  File
"/gnu/store/9qknps8svnw5njfr823bm1il1gw5nxlm-python2-future-0.18.2/lib/python2.7/site-packages/tkinter/__init__.py",
line 5, in <module>
    from Tkinter import *
  File
"/gnu/store/y14nmmzzcs2a6m2gnn2diak2gkf5v2av-python2-2.7.18/lib/python2.7/lib-tk/Tkinter.py",
line 39, in <module>
    import _tkinter # If this fails your Python may not be configured for Tk
ImportError: No module named _tkinter
...trying to load module winreg: ERROR:
Traceback (most recent call last):
  File "/gnu/store/nwwr89v2vyg1hs48i49m083vhczsgh3m-sanity-check.py", line
69, in <module>
    importlib.import_module(name)
  File
"/gnu/store/y14nmmzzcs2a6m2gnn2diak2gkf5v2av-python2-2.7.18/lib/python2.7/importlib/__init__.py",
line 37, in import_module
    __import__(name)
  File
"/gnu/store/9qknps8svnw5njfr823bm1il1gw5nxlm-python2-future-0.18.2/lib/python2.7/site-packages/winreg/__init__.py",
line 6, in <module>
    from _winreg import *
ImportError: No module named _winreg
...trying to load module xmlrpc: OK
...trying to load endpoint console_scripts pasteurize: OK
...trying to load endpoint console_scripts futurize: OK
error: in phase 'sanity-check': uncaught exception:
%exception #<&invoke-error program: "python" arguments:
("/gnu/store/nwwr89v2vyg1hs48i49m083vhczsgh3m-sanity-check.py"
"/gnu/store/9qknps8svnw5njfr823bm1il1gw5nxlm-python2-future-0.18.2/lib/python2.7/site-packages")
exit-status: 1 term-signal: #f stop-signal: #f>
phase `sanity-check' failed after 0.2 seconds
command "python"
"/gnu/store/nwwr89v2vyg1hs48i49m083vhczsgh3m-sanity-check.py"
"/gnu/store/9qknps8svnw5njfr823bm1il1gw5nxlm-python2-future-0.18.2/lib/python2.7/site-packages"
failed with status 1