Android: set sys.platform to android

[vstinner]

BPO	32637
Nosy	@brettcannon, @doko42, @vstinner, @pmp-p, @yan12125, @xgid
PRs	bpo-32637: Set sys.platform to "android" on Android #5287 bpo-32637: Set sys.platform to "android" on Android #5288

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2018-05-29.21:47:52.520>
created_at = <Date 2018-01-23.17:16:49.050>
labels = ['3.7', 'library']
title = 'Android: set sys.platform to android'
updated_at = <Date 2018-05-29.21:47:52.519>
user = 'https://github.com/vstinner'

bugs.python.org fields:

activity = <Date 2018-05-29.21:47:52.519>
actor = 'vstinner'
assignee = 'none'
closed = True
closed_date = <Date 2018-05-29.21:47:52.520>
closer = 'vstinner'
components = ['Library (Lib)']
creation = <Date 2018-01-23.17:16:49.050>
creator = 'vstinner'
dependencies = []
files = []
hgrepos = []
issue_num = 32637
keywords = ['patch']
message_count = 6.0
messages = ['310511', '310516', '310537', '310543', '310594', '318102']
nosy_count = 6.0
nosy_names = ['brett.cannon', 'doko', 'vstinner', 'pmpp', 'yan12125', 'xgdomingo']
pr_nums = ['5287', '5288']
priority = 'normal'
resolution = 'out of date'
stage = 'resolved'
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue32637'
versions = ['Python 3.7']

[vstinner]

Currently, sys.platform and os.name are equal to 'linux' on Android. While Android uses the Linux kernel, the operating system is not a regular Linux. The libc (bionic) is very different than the regular glibc, the filesystem is organized very differently, etc.

I propose to change sys.platform and os.name to 'android' when running on Android.

[vstinner]

Wait, os.name is 'posix' on Android. That's fine in fact. Only sys.platform should be updated.

[vstinner]

The idea was first discussed on python-dev:

https://mail.python.org/pipermail/python-dev/2018-January/151874.html

me: "It seems like sys.platform == 'android' would be more appropriate
since Android is not Linux: different libc, different filesystems,
etc."

https://mail.python.org/pipermail/python-dev/2018-January/151887.html

Brett Cannon: "I've had a similar thought myself.".

[vstinner]

A similar change was proposed by pmp-p on MicroPython: micropython/micropython#3564

His use case is to use ffi module on Android (see the PR for more information), currently ffi fails to locate libraries.

[vstinner]

I propose to leave MACHDEP unchanged: keep MACHDEP="linux". Can it create inconsistencies? Is it an issue in practice?

My short term goal is to use sys.platform == 'android' has the reference test to check if we are running on Android.

[vstinner]

Sadly, I failed to find anyone to help me on this issue and I lost interest on supporting Android, so I just close the issue. Sorry.