error with grid functions guessing dimRange
See example: example.py. When the dimRange of a function is not given, it is guessed by putting in a dummy x and looking at the length of the return value (see dune/fempy/py/grid/function.hh:249). By default x == 0, which can cause python to give a dividing by zero error (seems to affect only python3.5, not python2.7). This error should either be ignored, or have some way for C++ to process this error properly, so the user knows to pass in the dimRange instead.