There's a bit of LaTeX math code in a comment in a test file:
```
.. math:: L = 10 \cdot \\log_{10}{\\left(\\frac{MS}{p_r^2} \\right)}
```
which of course should be `\\cdot`.
I could patch it, but I think skipping deprecation warnings in tests is
probably ok... (If nothing else it's easier.)
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`.
