Issue: pycscope -i 'srclistfile' python 3.7

[cjhawes]

When executing pycscope -i 'srclistfile' an error occurs. It seems that the string.rstrip section of line 118 in init.py brings up the error "string has no attribute rstrip".

I personally fixed this by changing that section to read "str.rstrip" and now the -i function works fine.