sympy/sympy — pull request #1021 by smichr (2012-01-25 04:37:22+00:00)
Title: 1707: raise NotimplementedError in evalf_atan

When evalf returns None, None, None, None in evalf_atan, raiseing
a ValueError allows the evalf fallback to continue for the
integral mentioned in issue 1707.

I'm not sure what the best error to raise is, but whatever is raised
has to be caught in the main evalf routine.

All tests pass in evalf. I haven't run the full suite, however.