Use a wrapper around xml.etree.ElementTree.fromstring in python 2.x (#7178)

Attributes aren't unicode objects, so they couldn't be directly used in info_dict fields (for example '--write-description' doesn't work with bytes).

youtube_dl/extractor/vevo.py

@@ -1,10 +1,10 @@
 from __future__ import unicode_literals
 
 import re
-import xml.etree.ElementTree
 
 from .common import InfoExtractor
 from ..compat import (
+    compat_etree_fromstring,
     compat_urllib_request,
 )
 from ..utils import (
@@ -97,7 +97,7 @@ class VevoIE(InfoExtractor):
         if last_version['version'] == -1:
             raise ExtractorError('Unable to extract last version of the video')
 
-        renditions = xml.etree.ElementTree.fromstring(last_version['data'])
+        renditions = compat_etree_fromstring(last_version['data'])
         formats = []
         # Already sorted from worst to best quality
         for rend in renditions.findall('rendition'):
@@ -114,7 +114,7 @@ class VevoIE(InfoExtractor):
 
     def _formats_from_smil(self, smil_xml):
         formats = []
-        smil_doc = xml.etree.ElementTree.fromstring(smil_xml.encode('utf-8'))
+        smil_doc = compat_etree_fromstring(smil_xml.encode('utf-8'))
         els = smil_doc.findall('.//{http://www.w3.org/2001/SMIL20/Language}video')
         for el in els:
             src = el.attrib['src']