(cherry picked from commit 7bd21d3)

Not distributing dependencies via hydraPlatforms does not work,
so we keep meta simple.

(cherry picked from commit 4643796)

Python packages set: patch updates

…docs

ghc8102BinaryMinimal: fix docs as legally required

…Modules

requiredPythonModules is already an attribute in the (passthru of the)
builder.

…`propagatedBuildInputs`

Python programs look up their dependencies dynamically. To support this,
Python executables are wrapped and patched.

To find the dependencies to include when wrapping and patching, the
`wrapPythonPrograms` function would traverse the
`propagatedBuildInputs`. `propagatedBuildInputs` are dependencies that
need to be propagated during *build time*. While that is needed, we do
not want to have *all* propagated build inputs always as run-time
dependencies. Therefore, many derivations instead choose to set
`pythonPath`, which `wrapPythonPrograms` also considers.`pythonPath`,
however, is just an attribute that is not recursed into.

This commit implements `requiredPythonModules`, which was already set in
the `passthru` of Python packages for
`python.buildEnv`/`python.withPackages`. Now, it is also passed to the
builder, and `wrapPythonPrograms` will consider this environment
variable instead of `propagatedBuildInputs`. This change will thus
prevent unwanted bloat in wrappers. It also effectively replaces
`pythonPath`. Note we could have used `pythonPath` for this, but I want
to avoid that name because what we do is not exactly what `PYTHONPATH`
does.

Builders other than `buildPythonPackage` will typically need to pass
something like

requiredPythonModules = with python3.pkgs;
computeRequiredPythonModules [ sphinx ];

for run-time Python dependencies.

This change is a prerequisite to unifying how we deal with wrappers in
Nixpkgs. E.g., now we can look into a common method for dealing with
wrappers for Qt, Python and GApps without getting bloat from Python
packages.

TODO: update documentation

buildPython*: drop support for pythonPath

buildPythonPackage: add note regarding propagation

buildPython*: write requiredPythonModules to nix-support/

We would like to keep references to run-time dependencies. Before, this
was done with `propagatedBuildInputs` resulting in
`nix-support/propagated-build-inputs`.

This is also another step towards getting rid of `propagatedBuildInputs`.

…edBuildInputs

Python packages should now use `requiredPythonModules` to declare their
runtime dependencies.

Note in some cases there may have been good reasons to put a non-Python
package in `propagatedBuildInputs`. In that case, a manual change needs
to be made to put that package back into `propagatedBuildInputs`.

These are now effectively the same.

These are the ones explicitly invoking wrapPythonProgramsIn with
pythonPath. Need to test this.

`wrapPython` will already extend PATH with the bin/ of each Python
dependency. We should do the same for non-Python dependencies.

Replace pythonPath with requiredPythonModules for non-buildPython*
packages.

In this case, it is just a name of the attribute, and it does not matter
what it is because `wrapPythonProgramsIn` is invoked explicitly.

In a future commit wrapPython hook will be replaced by one that does not
require an explicit invocatoin of `wrapPythonProgramsIn`.

Now that Python packages should use `requiredPythonModules` instead of
`propagatedBuildInputs`, we could actually check it during evaluation time.

This commit adds a warning in case Python modules are propagated. Now, in
principle it is fine to propagate modules, but there is not really any
good reason for it.

Note application propagation is not affected by this because in that case
`drv.pythonModule` is `false` or missing.

BuildPython* no longer propagates dependencies that way.

since its no longer propagated.