it's not possible to have two python parts

[Leo Arias]

With the recent fix for python in classic [1], now each python part installs packages using parts/{part}/install/usr/bin/python. This causes the RECORD files to differ between the parts, and a conflict is caused when trying to put the two parts in the same snap.

To reproduce:

$ git clone https://github.com/snapcore/snapcraft /tmp/snapcraft
$ cd /tmp
$ mkdir bug
$ cd bug
Make in this directory a snapcraft.yaml with two parts that only have:
source: .
plugin: python
(there is one attached)
$ /tmp/snapcraft/bin/snapcraft

Parts 'p1' and 'p2' have the following file paths in common which have different contents:
    lib/python3.5/site-packages/pip-9.0.1.dist-info/RECORD
    lib/python3.5/site-packages/setuptools-34.1.1.dist-info/RECORD
    lib/python3.5/site-packages/wheel-0.29.0.dist-info/RECORD

Snapcraft offers some capabilities to solve this by use of the following keywords:
    - `filesets`
    - `stage`
    - `snap`
    - `organize`

Learn more about these part keywords by running `snapcraft help plugins`

[1] https://github.com/snapcore/snapcraft/pull/1093/files

[Leo Arias (elopio)]

https://github.com/snapcore/snapcraft/pull/1138