more pythonic way to find 'fatal' in string

use 'in' instead of find.

gitstatus.py

@@ -14,14 +14,14 @@
 
 error_string = error.decode('utf-8')
 
-if error_string.find('fatal: Not a git repository') != -1:
+if 'fatal: Not a git repository' in error_string:
 	sys.exit(0)
 
 branch = branch.strip()[11:]
 
 res, err = Popen(['git','diff','--name-status'], stdout=PIPE, stderr=PIPE).communicate()
 err_string = err.decode('utf-8')
-if err_string.find('fatal') != -1:
+if 'fatal' in err_string:
 	sys.exit(0)
 changed_files = [namestat[0] for namestat in res.splitlines()]
 staged_files = [namestat[0] for namestat in Popen(['git','diff', '--staged','--name-status'], stdout=PIPE).communicate()[0].splitlines()]