Drop py2 support in gs-related files

python3 is the only supported version of python in depot_tools.

Bug: 1475402
Change-Id: I71db631b5556525dd4932134679c70cacd205a90
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/4824616
Reviewed-by: Josip Sokcevic <sokcevic@chromium.org>
Commit-Queue: Gavin Mak <gavinmak@google.com>
diff --git a/gsutil.py b/gsutil.py
index 85b72bf..c8eb0ff 100755
--- a/gsutil.py
+++ b/gsutil.py
@@ -18,11 +18,7 @@
 import sys
 import tempfile
 import time
-
-try:
-  import urllib2 as urllib
-except ImportError:  # For Py3 compatibility
-  import urllib.request as urllib
+import urllib.request
 
 import zipfile
 
@@ -65,7 +61,7 @@
     local_md5 = md5_calc.hexdigest()
 
     metadata_url = '%s%s' % (API_URL, filename)
-    metadata = json.load(urllib.urlopen(metadata_url))
+    metadata = json.load(urllib.request.urlopen(metadata_url))
     remote_md5 = base64.b64decode(metadata['md5Hash']).decode('utf-8')
 
     if local_md5 == remote_md5:
@@ -74,7 +70,7 @@
 
   # Do the download.
   url = '%s%s' % (GSUTIL_URL, filename)
-  u = urllib.urlopen(url)
+  u = urllib.request.urlopen(url)
   with open(target_filename, 'wb') as f:
     while True:
       buf = u.read(4096)