Update tools/ modules for compatibility with python 3.

Fixes #4097.
Fixes part of #4310.

Closes #4265.

PiperOrigin-RevId: 179437184
diff --git a/tools/objc/protobuf_compiler.py b/tools/objc/protobuf_compiler.py
index bd789b7..bc99093 100644
--- a/tools/objc/protobuf_compiler.py
+++ b/tools/objc/protobuf_compiler.py
@@ -15,8 +15,10 @@
 
 """Dummy python executable."""
 
+from __future__ import print_function
+
 import sys
 
 if __name__ == '__main__':
-  print 'Bazel does not yet support protobuf compiling.'
+  print('Bazel does not yet support protobuf compiling.')
   sys.exit(1)