sympy/sympy — pull request #8505 by GitRay (2014-11-23 04:03:59+00:00)
Title: fixes #7840

Be gentle, I've never done this before. This fixes a problem where cse subs out the final "True" statement in a Piecewise. This fix prevents cse from ever creating a "x0 == True" or "x0 == False" replacement, which I don't think is ever helpful.