Split buildPythonPackage into setup hooks

This commit splits the `buildPythonPackage` into multiple setup hooks.

Generally, Python packages are built from source to wheels using `setuptools`.
The wheels are then installed with `pip`. Tests were often called with
`python setup.py test` but this is less common nowadays. Most projects
now use a different entry point for running tests, typically `pytest`
or `nosetests`.

Since the wheel format was introduced more tools were built to generate these,
e.g. `flit`. Since PEP 517 is provisionally accepted, defining a build-system
independent format (`pyproject.toml`), `pip` can now use that format to
execute the correct build-system.

In the past I've added support for PEP 517 (`pyproject`) to the Python
builder, resulting in a now rather large builder. Furthermore, it was not possible
to reuse components elsewhere. Therefore, the builder is now split into multiple
setup hooks.

The `setuptoolsCheckHook` is included now by default but in time it should
be removed from `buildPythonPackage` to make it easier to use another hook
(curently one has to pass in `dontUseSetuptoolsCheck`).

pkgs/development/python-modules/wheel/default.nix

@@ -1,15 +1,19 @@
 { lib
+, setuptools
+, pip
 , buildPythonPackage
 , fetchPypi
 , pytest
 , pytestcov
 , coverage
 , jsonschema
+, bootstrapped-pip
 }:
 
 buildPythonPackage rec {
   pname = "wheel";
   version = "0.33.4";
+  format = "other";
 
   src = fetchPypi {
     inherit pname version;
@@ -17,14 +21,14 @@ buildPythonPackage rec {
   };
 
   checkInputs = [ pytest pytestcov coverage ];
+  nativeBuildInputs = [ bootstrapped-pip setuptools ];
 
-  propagatedBuildInputs = [ jsonschema ];
-
+  catchConflicts = false;
   # No tests in archive
   doCheck = false;
 
   # We add this flag to ignore the copy installed by bootstrapped-pip
-  installFlags = [ "--ignore-installed" ];
+  pipInstallFlags = [ "--ignore-installed" ];
 
   meta = {
     description = "A built-package format for Python";