Support Python 3

[astrofrog]

At the moment, gmvault does not run on Python 3:

Traceback (most recent call last):
  File "/tmp/gmvault.bootstrap.63252", line 1, in <module>
    import gmv.gmv_cmd as runner
  File "/Users/tom/miniconda3/envs/production/lib/python3.4/site-packages/gmv/gmv_cmd.py", line 455
    except Exception, _: #pylint:disable=W0703
                    ^
SyntaxError: invalid syntax

I'd be happy to help with supporting Python 3 if needed.

[gaubert]

@astrofrog Yes that would be great. Just create your own branch and start transforming the code to make it compliant. This shouldn't be too complex. Then we will have to think about unicode issues.

[gaubert]

@astrofrog Did you start working on it ? This is remove most of the unicode issues and that would be great.

[astrofrog]

@gaubert I haven't had a chance yet. I will have time again in October to try and work on this, but if anyone else wants to work on this in the mean time, please don't let me stop you! :)

[karanrajpal14]

I'm still facing this issue. Has it been fixed recently @astrofrog ?

[astrofrog]

@karanrajpal14 - I haven't had a chance to help with this

[nestukh]

Debian Bullseye (next stable release of Debian, probably out later this year) will drop support to Python 2:
https://en.wikipedia.org/wiki/Debian_version_history#Debian_11_(Bullseye)
Pip 21.0 has dropped support for Python 2.7 in January 2021:
https://pip.pypa.io/en/latest/development/release-process/#python-2-support
In fact, you can upgrade pip up to version 20.3 and no further in py2 enviroments.
Surely it will be still installable using workarounds, but gmvault is the last program I personally use not yet on 3.
It would be nice to have gmvault on Python 3 too.
I don't have time to contribute, I only know that the utility 2to3 helped me a lot on this matter on various projects.

[nestukh]

I've mentioned a workaround in #352 (comment)