Nixpkgs: Notmuch fails to build on master

[hedning]

notmuch fails to build on master, after the last staging-next merge. It's a failing test, but one that's reproducible and suggests something is actually wrong (ie. python version mixup):

Failing test

 FAIL   Handle files vanishing between scandir and add_file
        --- T050-new.36.EXPECTED        2018-12-09 10:43:07.572628337 +0000
        +++ T050-new.36.OUTPUT  2018-12-09 10:43:07.574628350 +0000
        @@ -1,4 +1,14 @@
        -Unexpected error with file /build/notmuch-0.28/test/tmp.T050-new/mail/vanish
        -add_file: Something went wrong trying to read or write a file
        -Error opening /build/notmuch-0.28/test/tmp.T050-new/mail/vanish: No such file or directory
        -exit status: 75
        +Fatal Python error: initsite: Failed to import the site module
        +Traceback (most recent call last):
        +  File "/nix/store/wvfm7149wwdmgyhcyfq9zmxiy9wbq7zb-python2.7-setuptools-40.4.3/lib/python2.7/site-packages/site.py", line 73, in <module>
        +    __boot()
        +  File "/nix/store/wvfm7149wwdmgyhcyfq9zmxiy9wbq7zb-python2.7-setuptools-40.4.3/lib/python2.7/site-packages/site.py", line 26, in __boot
        +    import imp  # Avoid import loop in Python 3
        +  File "/nix/store/yxiqcxi4ml1k7v7yxsfcwarji2w551bc-python3-3.7.1/lib/python3.7/imp.py", line 27, in <module>
        +    import tokenize
        +  File "/nix/store/yxiqcxi4ml1k7v7yxsfcwarji2w551bc-python3-3.7.1/lib/python3.7/tokenize.py", line 33, in <module>
        +    import re
        +  File "/nix/store/yxiqcxi4ml1k7v7yxsfcwarji2w551bc-python3-3.7.1/lib/python3.7/re.py", line 143, in <module>
        +    class RegexFlag(enum.IntFlag):
        +AttributeError: module 'enum' has no attribute 'IntFlag'
        +exit status: 1

I highly suspect that it's due to glib now using python3 (after gnome 3.30 upgrade) and (gmime3)[https://github.com/NixOS/nixpkgs/blob/master/pkgs/development/libraries/gmime/3.nix] propagating glib.

Switching notmuch to python3 resolves the issue, though I'm not sure if that's safe, as there might be things depending on notmuch's python2 bindings.

cc most recent maintainer @flokli

[flokli]

I think only afew and alot inside nixpkgs use the python bindings, while we already pass python3Packages as pythonPackages into pkgs/applications/networking/mailreaders/afew/default.nix.

alot seems to support python 3 too, and will discontinue python 2 support for the next release.

@hedning can you pass python3 to notmuch, and to alot too (similar to how it's done with afew), and see if this works for you?

[hedning]

afew is already using python3 5f03d6bf4d19714fec880729b946110799dd39db (Edit: can't read...)

alot doesn't support python3 yet: https://github.com/pazz/alot/releases/tag/0.7

[hedning]

Yeah, I'm getting this when trying to build alot with python3:

Processing ./alot-0.7-py3-none-any.whl
alot requires Python '>=2.7,<3.0' but the running Python is 3.7.1

[domo141]

In case of notmuch tests, it is possible that some of the PYTHON* environment variables
we set confuses gdb which python extension is using python 2.7.

(or then not, the log below ( https://hydra.nixos.org/build/85712357/nixlog/1 ) shows mixup of python 2.7 and 3.7 ...)

    +Fatal Python error: initsite: Failed to import the site module
        +Traceback (most recent call last):
        +  File "/nix/store/wvfm7149wwdmgyhcyfq9zmxiy9wbq7zb-python2.7-setuptools-40.4.3/lib/python2.7/site-packages/site.py", line 73, in <module>
        +    __boot()
        +  File "/nix/store/wvfm7149wwdmgyhcyfq9zmxiy9wbq7zb-python2.7-setuptools-40.4.3/lib/python2.7/site-packages/site.py", line 26, in __boot
        +    import imp  # Avoid import loop in Python 3
        +  File "/nix/store/yxiqcxi4ml1k7v7yxsfcwarji2w551bc-python3-3.7.1/lib/python3.7/imp.py", line 27, in <module>
        +    import tokenize
        +  File "/nix/store/yxiqcxi4ml1k7v7yxsfcwarji2w551bc-python3-3.7.1/lib/python3.7/tokenize.py", line 33, in <module>
        +    import re
        +  File "/nix/store/yxiqcxi4ml1k7v7yxsfcwarji2w551bc-python3-3.7.1/lib/python3.7/re.py", line 143, in <module>
        +    class RegexFlag(enum.IntFlag):
        +AttributeError: module 'enum' has no attribute 'IntFlag'

[gebner]

alot 0.8 now requires python 3. I've updated alot, and used python 3 for notmuch.

I've tried neomutt and alot and they both work.