Certain programs, like zim, calibre and now also apparently mercurial,
rely on sys.argv[0] providing not just the script name but the full
path.
The Python docs [1] state the following on the matter:
> argv[0] is the script name (it is operating system dependent whether
this is a full pathname or not).
Therefore, scripts should not expect to receive a full path.
Unfortunately some do. While this can be considered a bug, there doesn't
seem any reason not to provide the full path. Therefore we now provide
the full path.
[1]
https://docs.python.org/3.5/library/sys.html?highlight=sys.argv#sys.argv
A package set is constructed for a specific interpreter. Therefore, we add the
possibility to override the package set to the interpreter. This should make it
easier to override the interpreter and the package set at the same time.
In #19309 a separate output for tkinter was added.
Several dependencies of Python depend indirectly on Python. We have the
following two paths:
```
‘python-2.7.12’ - ‘tk-8.6.6’ - ‘libXft-2.3.2’ - ‘libXrender-0.9.10’ -
‘libX11-1.6.4’ - ‘libxcb-1.12’ - ‘libxslt-1.1.29’- ‘libxml2-2.9.4’ -
‘python-2.7.12’
‘python-2.7.12’ - ‘tk-8.6.6’ - ‘libXft-2.3.2’ - ‘fontconfig-2.12.1’ -
‘dejavu-fonts-2.37’ - ‘fontforge-20160404’ - ‘python-2.7.12’
```
Because only `tkinter` needs this, I added
```
pythonSmall = python.override {x11Support = false;};
```
to break the infinite recursion. We also still have the output
`tkinter`.
However, we might as well build without x11Support by default. Then we build with x11Support as well so we get the tkinter module and put that in a separate package.
python.buildenv is used to build an env that provides binaries that can
import all modules that were passed in to the env.
Before this change it filtered the propagatedBuildInputs to remove all
non-Python packages, thereby possibly reducing the amount of packages
that were referenced. However, Python packages often don't have non-
Python packages as propagatedBuildInputs. And occasionally, we do want
to be able to add other packages to the env.
