Use sys.exit(...) instead of exit(...): exit(...) should not be used in programs

contrib/devtools/check-doc.py

@@ -12,6 +12,7 @@ Author: @MarcoFalke
 
 from subprocess import check_output
 import re
+import sys
 
 FOLDER_GREP = 'src'
 FOLDER_TEST = 'src/test/'
@@ -39,7 +40,7 @@ def main():
   print "Args unknown     : %s" % len(args_unknown)
   print args_unknown
 
-  exit(len(args_need_doc))
+  sys.exit(len(args_need_doc))
 
 if __name__ == "__main__":
     main()