Bump pylint to pylint-1.9.2

tools/distrib/pylint_code.sh

@@ -1,5 +1,5 @@
 #!/bin/bash
-# Copyright 2017 gRPC authors.
+# Copyright 2017 The gRPC Authors
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
@@ -35,7 +35,7 @@ python -m virtualenv $VIRTUALENV
 PYTHON=$VIRTUALENV/bin/python
 
 $PYTHON -m pip install --upgrade pip==10.0.1
-$PYTHON -m pip install pylint==1.6.5
+$PYTHON -m pip install pylint==1.9.2
 
 for dir in "${DIRS[@]}"; do
   $PYTHON -m pylint --rcfile=.pylintrc -rn "$dir" || exit $?