Update git submodules

* Update tools/repohooks from branch 'master'
  to ce3ab294550d3faf1adb8c55f6cb87c516321221
  - sixish: handle Unicode strings in the environment
    
    Python 2 wants ASCII/bytes (not unicode strings) while Python 3 wants
    strings (not bytes).  Add a helper to deal with this on the fly.
    
    Bug: None
    Test: unittests pass
    Change-Id: Ic28182608647973749390e3a66731472a2010c35
    
1 file changed