depot_tools: Make git_cache Python 3 compatible.

Bug: 984182
Change-Id: Ia413435af80d03dcfa01bb2ab7480cd6a37b4161
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/1717496
Reviewed-by: Andrii Shyshkalov <tandrii@chromium.org>
Commit-Queue: Edward Lesmes <ehmaldonado@chromium.org>
diff --git a/git_cache.py b/git_cache.py
index c116630..45c63b4 100755
--- a/git_cache.py
+++ b/git_cache.py
@@ -537,6 +537,7 @@
         [self.git_exe, 'config', '--get-all', 'remote.origin.fetch'],
         cwd=rundir).strip().splitlines()
     for spec in fetch_specs:
+      spec = spec.decode()
       try:
         self.print('Fetching %s' % spec)
         with self.print_duration_of('fetch %s' % spec):
@@ -885,4 +886,4 @@
     sys.exit(main(sys.argv[1:]))
   except KeyboardInterrupt:
     sys.stderr.write('interrupted\n')
-    sys.exit(1)
\ No newline at end of file
+    sys.exit(1)