STY: standardize spacing for casting, with linting
Casting in cython is done with the syntax `<type>obj` or `<type> obj`.  ATM the code uses both of these.  This PR standardizes on the first usage, with a lint check.

@datapythonista I'm not sure whether the grep check here belongs in the patterns section or in the non-python section.  LMK if you have a preference.