Move MediaGoblin to Python 3

[Christopher Allan Webber]

It should be more or less possible to move MediaGoblin to Python 3, which of course means that we should! This bug exists to track the efforts to do so.

[Christopher Allan Webber]

So, current evaluation of dependencies:

| Library            | py3? | notes                               |
|--------------------+------+-------------------------------------|
| setuptools         | X    | Distribute                          |
| PasteScript        |      | not *technically* necessary         |
| wtforms            | X    |                                     |
| py-bcrypt          | X    |                                     |
| pytest>=2.3.1      | X    |                                     |
| pytest-xdist       | ??   |                                     |
| werkzeug>=0.7      | X    |                                     |
| celery>=3.0        | X    |                                     |
| kombu              | X    |                                     |
| jinja2             | X    |                                     |
| sphinx             | X    |                                     |
| Babel<1.0          | X    |                                     |
| argparse           | X    |                                     |
| webtest<2          | X    |                                     |
| ConfigObj          |      | unofficial port exists from 2010... |
| Markdown           | X    |                                     |
| sqlalchemy>=0.8.0  | X    |                                     |
| sqlalchemy-migrate |      | unmaintained anyhow :\              |
| mock               | X    |                                     |
| itsdangerous       | X    |                                     |
| pytz               | X    |                                     |
| six                | X    |                                     |
| oauthlib==0.5.0    | X    |                                     |

Most of these are converted to Python 3. Of the ones that aren't:

• We technically don't need PasteScript and don't use it for anything other than the entry point to use PasteDeploy with an http server. That's easily replaced, and maybe this should be a gmg command anyway.
• ConfigObj has ​an unofficial port but it's not "officially blessed". We could package this and put it on PyPi on our own if we need to, but someone should contact the author(s) about that. (does anyone volunteer?)
• The biggest headache will be sqlalchemy-migrate. However, sqlalchemy-migrate is unmaintained anyhow, so we should probably move to ​Alembic. The biggest question with Alembic is whether or not it will support sqlite? (Could someone research this?)

The best way to start this project would be to probably do, in order:

• Start porting MediaGoblin's code to python 3 generally. Ignore migrations, just support MediaGoblin "starting with the latest database schema", or even easier, set up your database on the python 2 branch before you git checkout the python 3 branch. ;)
• As for getting an entry point to PasteDeploy, I can help with that.
• Sort out what to do about packaging ConfigObj for python 3
• Finally, look at the future of migrations. (That should be its own bug probably?)

[Christopher Allan Webber]

exif.py python 3 port also: ​http://exif-py-3.sourceforge.net/

[berkerpeksag]

Update to the original dependency list:

• PasteScript has Python support on my branch at ​https://bitbucket.org/berkerpeksag/pastescript/commits/240083e50012bb3fdf57bdf13bec32a8b5d3872c
• pytest-xdist has Python 3 support as of version 1.5.
• ConfigObj is officially maintained by Eli Courtwright and Rob Dennis on GitHub: ​https://github.com/DiffSK/configobj

Other blockers

Media types

• scikits.audiolab doesn't have Python 3 support yet, but there is a WIP branch on GitHub: ​https://github.com/cournape/audiolab/issues/24

Plugins:

• python-ldap: There is python3-ldap package on PyPI, but its API is incompatible with python-ldap.
• python-openid: python3-openid is compatible with python-openid

[berkerpeksag]

There is a single codebase port of exifread on GitHub:

• ​https://github.com/ianare/exif-py/tree/develop (the original author)

Also, here's my progress so far:

3 failed, 123 passed, 4 skipped in 129.58 seconds

[Christopher Allan Webber]

Done. We've merged this into master.

[Christopher Allan Webber]

Also, super exciting! Thank you again Berker! :)