python: Use the unicode_escape codec

Python 2 had string_escape and unicode_escape codecs. Python 3 only has
the latter. These work the same as far as we're concerned, so let's use
the future-proof one.

However, the reste of the code expects unicode strings, so we need to
decode them again.

Signed-off-by: Mathieu Bridon <bochecha@daitauha.fr>
Reviewed-by: Dylan Baker <dylan@pnwbakers.com>

src/amd/common/sid_tables.py

@@ -65,7 +65,7 @@ class StringTable:
         """
         fragments = [
             '"%s\\0" /* %s */' % (
-                te[0].encode('string_escape'),
+                te[0].encode('unicode_escape').decode(),
                 ', '.join(str(idx) for idx in sorted(te[2]))
             )
             for te in self.table

src/gallium/drivers/r600/egd_tables.py

@@ -61,7 +61,7 @@ class StringTable:
         """
         fragments = [
             '"%s\\0" /* %s */' % (
-                te[0].encode('string_escape'),
+                te[0].encode('unicode_escape').decode(),
                 ', '.join(str(idx) for idx in te[2])
             )
             for te in self.table