```
WARNING: Retrying (Retry(total=0, connect=None, read=None, redirect=None, status=None)) after connection broken by 'NewConnectionError('<pip._vendor.urllib3.connection.VerifiedHTTPSConnection object at 0x7ffff642da90>: Failed to establish a new connection: [Errno -2] Name or service not known',)': /simple/pytest-codestyle/
ERROR: Could not find a version that satisfies the requirement pytest-codestyle (from versions: none)
ERROR: No matching distribution found for pytest-codestyle
```
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`.
