grit: c_format: use %o to avoid weird parsing

We're running an integer through oct() to get a string of the octal
number, which we then pass to int() to parse as a decimal number so
we can finally pass to %d to get a padded string.
  195 -> '0303' -> 303 -> '303'

This relies on the exact output format of oct() which breaks when
using Python 3 -- it outputs '0o303' which int() rejects.

We can simplify this greatly by just switching from %d to %o and
letting Python do the translation for us.

Bug: 983071
Test: `./grit/test_suite_all.py` passes
Change-Id: I9c379d0962819e69eed2890bc2369784c0a95ef3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1755384Reviewed-by: Robert Flack <flackr@chromium.org>
Commit-Queue: Mike Frysinger <vapier@chromium.org>
Cr-Commit-Position: refs/heads/master@{#687255}

tools/grit/grit/format/c_format.py

@@ -56,7 +56,7 @@ def _HexToOct(match):
   result = ""
   while len(hex):
     next_num = int(hex[2:4], 16)
-    result += "\\" + '%03d' % int(oct(next_num), 10)
+    result += "\\" + '%03o' % next_num
     hex = hex[4:]
   return match.group("escaped_backslashes") + result