1362323 - Upgrade to python 3.6

Status: ASSIGNED

Description

[Emin Mastizada]

After 3 years python 2.x will be discontinued. Also new features will not come to python 2.x anymore. Also python 3.x consumes less memory in string variables (optimized for Unicode) and works a bit faster.

# Statements in wiki[1]:

List of features that will not be backported to python 2.x:
* strings are Unicode by default
* clean Unicode/bytes separation
* exception chaining
* function annotations
* syntax for keyword-only arguments
* extended tuple unpacking
* non-local variable declarations

Heroku supports python-3.6.1 runtime. Some operating systems (Linux distributions) are already using python 3.x as default.

# What needs to be done:
1. Checking all dependencies for python 3.6 support.
2. Updating documentation (for example specifying python version for virtualenv as MacOS and some Linux distros are currently using python 2.x as default).
3. Checking and updating code to support it.

I'll be happy to work on it, but as it is a major change, it needs to be discussed. Mostly about what can be side effects and etc.

[1] https://wiki.python.org/moin/Python2orPython3

Comment 1

[Matjaz Horvat [:mathjazz]]

Thanks for filing, Emin!

I don't have enough insight right now, so I'm removing the NI.

Comment 2

[Axel Hecht [:Pike]]

As of dependencies, compare-locales isn't py3 yet, and I don't expect to invest in an update on that until we can use python3 in the firefox build system. translate-toolkit seems to be fine with py3.

Also, django 2 will not support python 2 (oh the irony).

Comment 3

[Osmose [:osmose, :mkelly]]

I don't have any major insight except "Yes, do this yesterday."

For dependencies like compare-locales, I'd recommend using six[1] to make them both Python 2 and Python 3 compatible. You can use tox[2] to help run your test suite under multiple versions of Python easily, as well.

[1] https://pythonhosted.org/six/
[2] https://tox.readthedocs.io/en/latest/

Comment 4

[Emin Mastizada]

Wiki to track updates: https://wiki.mozilla.org/L10n:Pontoon/Python_3
Pad: https://public.etherpad-mozilla.org/p/pontoon.python3

Comment 5

[Emin Mastizada]

depends on bug 1386193

Comment 6

[Matjaz Horvat [:mathjazz]]

An interesting read on how Socorro got migrated to Python 3:
https://bluesock.org/~willkg/blog/mozilla/socorro_python3.html

A note from Pike:
"Splitting up requirements into requirements and constraints sounds nice"