contrib: fromupstream: Fix quoting issues found by linter

Running 'cros lint fromupstream.py' after CL:1742539 yells:

 $ cros lint fromupstream.py
 ************* Module fromupstream
 C: 45, 0: Invalid string quote ", should be ' (invalid-string-quote)
 C:102, 0: Invalid string quote ', should be " (invalid-string-quote)
 C:219, 0: Invalid string quote ", should be ' (invalid-string-quote)
 C:341, 0: Invalid string quote ", should be ' (invalid-string-quote)

Let's fix them.

BUG=chromium:980619
TEST=cros lint is happy now

Change-Id: I46f355cb968c94c3ee5551fb137c6e3990822186
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/dev-util/+/1749861
Tested-by: Douglas Anderson <dianders@chromium.org>
Auto-Submit: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
Commit-Queue: Douglas Anderson <dianders@chromium.org>
Commit-Queue: Mike Frysinger <vapier@chromium.org>
diff --git a/contrib/fromupstream.py b/contrib/fromupstream.py
index 0aee900..6df47e6 100755
--- a/contrib/fromupstream.py
+++ b/contrib/fromupstream.py
@@ -42,7 +42,7 @@
         if resolution in resolutions:
             conflicts.append('   ' + name)
     if not conflicts:
-        return ""
+        return ''
     return '\nConflicts:\n%s\n' % '\n'.join(conflicts)
 
 def _find_linux_remote():
@@ -99,7 +99,7 @@
             sys.exit(1)
 
     if not config.has_option(project, 'url'):
-        sys.stderr.write('Error: patchwork URL not found for project \'%s\'\n'
+        sys.stderr.write("Error: patchwork URL not found for project '%s'\n"
                          % project)
         sys.exit(1)
 
@@ -216,7 +216,7 @@
                 args['tag'] = 'FROMLIST: '
 
             url = _get_pw_url(pw_project)
-            opener = urllib.urlopen("%s/patch/%d/mbox" % (url, patch_id))
+            opener = urllib.urlopen('%s/patch/%d/mbox' % (url, patch_id))
             if opener.getcode() != 200:
                 sys.stderr.write('Error: could not download patch - error code %d\n' \
                                  % opener.getcode())
@@ -338,7 +338,7 @@
                 args['tag'] = 'BACKPORT: ' + args['tag']
             _pause_for_merge(conflicts)
         else:
-            conflicts = ""
+            conflicts = ''
 
         # extract commit message
         commit_message = subprocess.check_output(