This reverts commit cc506381761d84bd0047cabba7151ad516fa8a32 because
it breaks cargo (again, see fca4fbeba957ec6bc72c98c019bbc5f01712d15b):
$ cargo build
Updating crates.io index
Segmentation fault
The `buildPython*` function computes name from `pname` and `version`.
This change removes `name` attribute from all expressions in
`pkgs/development/python-modules`.
While at it, some other minor changes were made as well, such as
replacing `fetchurl` calls with `fetchPypi`.
