Fixed E251 flake8 errors

unexpected spaces around keyword / parameter equals

_pytest/_code/source.py

@@ -198,8 +198,7 @@ class Source(object):
 # public API shortcut functions
 #
 
-def compile_(source, filename=None, mode='exec', flags=
-             generators.compiler_flag, dont_inherit=0):
+def compile_(source, filename=None, mode='exec', flags=generators.compiler_flag, dont_inherit=0):
     """ compile the given source to a raw code object,
         and maintain an internal cache which allows later
         retrieval of the source code for the code object