Cleanup pants.pex release version info

[jsirois]

There are two items to address:

1. The redundant version information in the released pex filename - just pants.pex is probably all that's needed.
2. A surprising version as reported by pants - does not match release:

   $ curl -LO https://github.com/pantsbuild/pants/releases/download/release_1.9.0.dev0/pants.1.9.0.dev0.pex && chmod +x pants.1.9.0.dev0.pex && ./pants.1.9.0.dev0.pex -V
     % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                    Dload  Upload   Total   Spent    Left  Speed
   100   609    0   609    0     0    904      0 --:--:-- --:--:-- --:--:--   904
   100 28.4M  100 28.4M    0     0  4050k      0  0:00:07  0:00:07 --:--:-- 6529k
   1.9.0.dev0+aad4b7be
   

[stuhood]

Should be able to use

pants/build-support/bin/release.sh

Line 410 in c5a46e9

function reversion_whls() {

[jsirois]

Yes, but I think that can be overhauled to use existing supported technology which may also help out over in #6022 as well.

Pants distillation with arbitrary version (using egg here just for ease of demonstration - works with wheel):

$ ./pants setup-py --run='egg_info -b+bob bdist_egg' src/python/pants:pants-packaged
$ PYTHONPATH=./dist/pantsbuild.pants-1.9.0.dev0/dist/pantsbuild.pants-1.9.0.dev0+bob-py2.7.egg python
Python 3.6.5 (default, May 11 2018, 04:00:52) 
[GCC 8.1.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import pkg_resources
>>> pkg_resources.get_distribution('pantsbuild.pants').version
'1.9.0.dev0+bob'
>>> 

3rdparty distillation with arbitrary version:

$ pip wheel --wheel-dir /tmp/distill --global-option egg_info --global-option -b+bob requests
$ tree /tmp/distill/
/tmp/distill/
├── certifi-2018.4.16+bob-py2.py3-none-any.whl
├── chardet-3.0.4+bob-py2.py3-none-any.whl
├── idna-2.7+bob-py2.py3-none-any.whl
├── requests-2.19.1+bob-py2.py3-none-any.whl
└── urllib3-1.23+bob-py2.py3-none-any.whl

Going to poke around a bit using this new-found (to me) tool.

[jsirois]

Noting this is the last known wart to pex publishing. The 1st publish by the CI Bot is live: https://github.com/pantsbuild/pants/releases/tag/release_1.9.0.dev1

[Eric-Arellano]

We both keep the version number and also encode the interpreter version, e.g. pants.1.28.0rc1.py36.pex. This is intentional. Consumers can rewrite the file name if they'd like.