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/bootstrapped-pip/default.nix

@@ -1,4 +1,8 @@
-{ stdenv, python, fetchPypi, makeWrapper, unzip }:
+{ stdenv, python, fetchPypi, makeWrapper, unzip, makeSetupHook
+, pipInstallHook
+, setuptoolsBuildHook
+
+}:
 
 let
   wheel_source = fetchPypi {
@@ -25,6 +29,15 @@ in stdenv.mkDerivation rec {
     sha256 = "993134f0475471b91452ca029d4390dc8f298ac63a712814f101cd1b6db46676";
   };
 
+  dontUseSetuptoolsBuild = true;
+
+  # Should be propagatedNativeBuildInputs
+  propagatedBuildInputs = [
+    # Override to remove dependencies to prevent infinite recursion.
+    (pipInstallHook.override{pip=null;})
+    (setuptoolsBuildHook.override{setuptools=null; wheel=null;})
+  ];
+
   unpackPhase = ''
     mkdir -p $out/${python.sitePackages}
     unzip -d $out/${python.sitePackages} $src
@@ -32,7 +45,7 @@ in stdenv.mkDerivation rec {
     unzip -d $out/${python.sitePackages} ${wheel_source}
   '';
 
-  patchPhase = ''
+  postPatch = ''
     mkdir -p $out/bin
   '';
 
@@ -52,4 +65,5 @@ in stdenv.mkDerivation rec {
       wrapProgram $f --prefix PYTHONPATH ":" $out/${python.sitePackages}/
     done
   '';
+
 }