BUG: Fix bugs in unused code paths.

The `getargspec` needed to import the disassembler to support parsing
tuple arguments. Since numpy never uses those, the corresponding code
is deleted and an TypeError raised if such arguments are encountered.

Also fix the unused formatargs function so it does not require the
string module.
STY: Minor PEP8 fixes.
Merge pull request #4941 from charris/fix-numpy-compat-_inspect

Fix numpy compat  _inspect