Fix python3 syntax

[aweimeow]

Yi: Originally this PR includes a change to the base container images. We will work on this part when we are updating the base image to Debian10.
For this PR we just fix some code syntax for Python3.

Original PR
Due to some weird reason, the container built by 2nd step will have the ANSI as default encoding, so I need to install locales and generate UTF-8 encoding for mininet script's emoji (☠️ & ⚡️). If we didn't change the encoding to UTF-8, it may cause python encoding exception.

Also includes the following changes:

• bump bazel version to 4.2.1
• bump default python version to 3.8.12
• completely remove python2
• Removee deprectaed dependency

[codecov]

Codecov Report

Merging #1 (787412f) into main (29f3915) will not change coverage.
The diff coverage is n/a.

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  Coverage   79.20%   79.20%           
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  Lines       30928    30928           
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  Hits        24496    24496           
  Misses       6432     6432           

[ccascone]

Hi @aweimeow, under which circumstances do you see python encoding exceptions? stratum.py has already the UTF-8 encoding special comment at the beginning of the file: https://github.com/stratum/stratum/blob/master/tools/mininet/stratum.py#L1

Bumping to python 3 might be abreaking change for anyone using this Docker image to run custom Mininet scripts. I'd rather find a fix that does not involve upgrading the Python version, or simply remove the emojis from the script...

[Yi-Tseng]

I think we can ask developers to move to py2 to py3, and officially drop python2 from this image on 2020/01/01.
The code change looks fine, it should work on both py2 and py3.

[aweimeow]

Hello @ccascone, although the stratum.py has the encoding header, if the terminal encoding didn't compatible with emoji character, it'll cause exception finally, here is a proof of concept.

aweimeow@MacBook-Pro:[~]$ cat test.py
# -*- coding: utf-8 -*-

print("☠️")
aweimeow@MacBook-Pro:[~]$ echo "$LANG $LC_CTYPE"
zh_TW.UTF-8 zh_TW.UTF-8
aweimeow@MacBook-Pro:[~]$ python test.py
☠️
aweimeow@MacBook-Pro:[~]$ LANG=ANSI LC_CTYPE=ANSI python test.py
Traceback (most recent call last):
  File "test.py", line 3, in <module>
    print("\u2620\ufe0f")
UnicodeEncodeError: 'ascii' codec can't encode characters in position 0-1: ordinal not in range(128)

I have no idea about which package or what command makes the new container's environment doesn't have UTF-8's encoding, so that is the reason for installing locales package to generate the corresponding language locale file.

About the upgrading to Python 3, I think it's necessary. There is a lot of famous Python 3rd library announced they won't support Python 2 after Python 2's EoL, despite stratum.py don't have many dependencies, but if the 3rd libraries have something wrong, we also can't get support on the failure.

From now to the Python 2 EoL, there have 3 months to go, if the upgrade causes the problem, the team still has time to fallback / fix the issue :)

[pudelkoM]

Closed due to inactivity. Feel free to reopen if you want to continue to work on this.

[Yi-Tseng]

Let's reopen this pull request since we think it is better to move to python3

[Yi-Tseng]

TODO:
delete the update_config.py since we already have pipeline builder

[bocon13]

lgtm

[aweimeow]

🎉🎉🎉

[bocon13]

Finally PR #1 is merged!! Thanks @aweimeow!