Make checkperms.py look for shebang.

tools/checkperms/checkperms.py

Index: tools/checkperms/checkperms.py
diff --git a/tools/checkperms/checkperms.py b/tools/checkperms/checkperms.py
index 2640d5a0ba2d59f2a6afc8d2cadf0be049626826..c3959f99ce9289fabcfae1a39588947cf89b9797 100755
--- a/tools/checkperms/checkperms.py
+++ b/tools/checkperms/checkperms.py
@@ -177,6 +177,12 @@ def CheckFile(file_path):
     return 'Failed to stat file: %s' % e
 
   if EXECUTABLE_PERMISSION & st_mode:
+    # Look if the file starts with #!/
+    with open(file_path, 'rb') as f:
+      if f.read(3) == '#!/':
+        # That's fine.
+        return None
+    # TODO(maruel): Check that non-executable file do not start with a shebang.
     error = 'Contains executable permission'
     if VERBOSE:
       return '%s: %06o' % (error, st_mode)