PEP8 compliance

Author: trevorkarn

src/sage/rings/polynomial/infinite_polynomial_element.py

@@ -525,7 +525,7 @@ def subs(self, fixed=None, **kwargs):
         try:
             return self(**kwargs)
         except TypeError:
-            str_kwargs = {str(k): v for k,v in kwargs.items()}
+            str_kwargs = {str(k): v for k, v in kwargs.items()}
             return self(**str_kwargs)
 
     def ring(self):