style: use import urllib.xxx everywhere

Align with Google style guides and `import urllib.xxx` as a module
rather than import symbols out of it.

Change-Id: Ia177f4fd5ee2a3f38f8a8860e9a2ba8beac8078f
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/654804
Reviewed-by: Brian Gan <brgan@google.com>
Tested-by: Mike Frysinger <vapier@google.com>
Commit-Queue: Mike Frysinger <vapier@google.com>

.flake8

@@ -7,7 +7,6 @@ per-file-ignores =
     # IMR241: When using the from syntax, only submodules are imported, not module elements.
     # NB: Do not add any more here.
     command.py: IMR241,
-    fetch.py: IMR241,
     git_command.py: IMR241,
     git_status.py: IMR241,
     git_superproject.py: IMR241,

fetch.py

@@ -16,8 +16,8 @@
 
 import subprocess
 import sys
-from urllib.parse import urlparse
-from urllib.request import urlopen
+import urllib.parse
+import urllib.request
 
 import error
 
@@ -32,7 +32,7 @@ def fetch_file(url, verbose=False):
     Returns:
         The contents of the file as bytes.
     """
-    scheme = urlparse(url).scheme
+    scheme = urllib.parse.urlparse(url).scheme
     if scheme == "gs":
         cmd = ["gcloud", "storage", "cat", url]
         errors = []
@@ -54,5 +54,5 @@ def fetch_file(url, verbose=False):
                 file=sys.stderr,
             )
         raise FetchFileError(aggregate_errors=errors)
-    with urlopen(url) as f:
+    with urllib.request.urlopen(url) as f:
         return f.read()