Checks if a ~= b * exp(i t) for some t.

actual A numpy array.
desired Another numpy array.
rtol Relative error tolerance.
atol Absolute error tolerance.
equal_nan Whether or not NaN entries should be considered equal to other NaN entries.
err_msg The error message to be printed in case of failure.
verbose If True, the conflicting values are appended to the error message.

AssertionError The matrices aren't nearly equal up to global phase.