sympy/sympy — pull request #2851 by skirpichev (2014-01-30 09:26:42+00:00)
Title: Better detection of zero-equivalence in calculate_series()

This pr, most likely, fixes the problem with test_wester.py/gruntz.py timeouts, mentioned in #2846. See also [my comment](https://github.com/sympy/sympy/pull/2846#issuecomment-33573790) in that thread.