Python: setuptools/wheel/pip now bootstrap from source

Since wheel support was introduced in 2015 we always relied on pre-built
wheels for bootstrapping. Now, we can bootstrap directly from the
sources of these packages in git.

The `bootstrapped-pip` packages is used to build `pip`, `setuptools` and `wheel`,
after which those packages are used to build everything else.

Note that when building `bootstrapped-pip` some errors are shown.
These are not important, the build actually does succeed and work as intended.

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

@@ -2,7 +2,7 @@
 , setuptools
 , pip
 , buildPythonPackage
-, fetchPypi
+, fetchFromGitHub
 , pytest
 , pytestcov
 , coverage
@@ -15,9 +15,12 @@ buildPythonPackage rec {
   version = "0.33.6";
   format = "other";
 
-  src = fetchPypi {
-    inherit pname version;
-    sha256 = "10c9da68765315ed98850f8e048347c3eb06dd81822dc2ab1d4fde9dc9702646";
+  src = fetchFromGitHub {
+    owner = "pypa";
+    repo = pname;
+    rev = version;
+    sha256 = "1bg4bxazsjxp621ymaykd8l75k7rvcvwawlipmjk7nsrl72l4p0s";
+    name = "${pname}-${version}-source";
   };
 
   checkInputs = [ pytest pytestcov coverage ];