Adapted test cases to Sympy Version 1.6
Due to Sympy Version 1.6 the sp.Abs function in the test_interpolation test cases could not be identified as integer anymore. This is now fixed by not checking the type of sp.Abs anymore but by checking its argument.
Furthermore depreciation warning fixes of pandas and pycuda and pytest and adaption to new flake8 Version.
Edited by Markus Holzer