sympy/sympy — pull request #7641 by smichr (2014-06-25 16:25:46+00:00)
Title: watch for improper separation of base and exp in powsimp

e.g. sqrt(x**a) should not be split as x**a, 1/2 otherwise
it will rejoin as x**(a/2) later -- this is noted with an
inline comment.