Fix python modules dependencies

The import statement must be enclosed in quotes.
Otherwise you get the outptut of https://gist.github.com/jaimeMF/775e6d09d9a90a779dbf.

This is the output when running the python command in bash:
```
$ /usr/bin/env python -c import nose
File "<string>", line 1
    import
         ^
SyntaxError: invalid syntax
```

Edited: I found it while installing matplotlib from the samueljohn/python tap.