Test to check bug in dsolve
Explicitly define variables in the polys benchmark

This avoids an enormous number of pyflakes errors for this file.
Explicitly define variables in bench_groebnertools.py
Merge pull request #2389 from asmeurer/polysbench

Explicitly define variables in the polys benchmark
Added @XFAIL test
Merge pull request #2379 from Manoj-Kumar-S/constant

Added XFAIL test for dsolve
Merge branch 'master' of git://github.com/sympy/sympy