sympy/sympy — pull request #873 by jcreus (2011-12-21 20:17:59+00:00)
Title: Fixing pyflakes errors from sympy.utilities (GCI)

I've cleared of errors the utilities module. (GCI Task: http://www.google-melange.com/gci/task/view/google/gci2011/7134380 ). I've used setup.py audit.

The warnings present aren't applicable/ok as they are. Here's the list.

```
sympy/utilities/pytest.py:53: redefinition of unused 'Skipped' from line 11
sympy/utilities/pytest.py:74: redefinition of unused 'skip' from line 13
sympy/utilities/pytest.py:146: redefinition of function 'XFAIL' from line 56
sympy/utilities/cythonutils.py:16: redefinition of function 'cythonized' from line 8
sympy/utilities/autowrap.py:253: local variable 'prototype_c' is assigned to but never used
sympy/utilities/iterables.py:6: 'cartes' imported but unused
sympy/utilities/lambdify.py:7: 'import_module' imported but unused
sympy/utilities/runtests.py:56: undefined name 'sys_case_insensitive'
sympy/utilities/runtests.py:844: local variable 'msg' is assigned to but never used
sympy/utilities/compilef.py:421: '_exp' imported but unused
sympy/utilities/compilef.py:421: '_cos' imported but unused
sympy/utilities/compilef.py:548: redefinition of unused '_exp' from line 421
sympy/utilities/compilef.py:548: redefinition of unused '_cos' from line 421
sympy/utilities/compilef.py:548: 'diff' imported but unused
sympy/utilities/decorator.py:7: 'Add' imported but unused
```
In many occasions, it is due to that some classes are written inside if/else, so according to PyFlakes they are "redefined". Others are simply necessary and errors appear without them.