Decode output from 'subprocess.check_output'

On Python 3, this returns a bytestring, which must be decoded to print
it correctly.

Signed-off-by: Stephen Finucane <[email protected]>
Closes: #43

Author: stephenfin

git_pw/utils.py

@@ -49,10 +49,10 @@ def git_am(mbox, args):
     try:
         output = subprocess.check_output(cmd, stderr=subprocess.STDOUT)
     except subprocess.CalledProcessError as exc:
-        print(exc.output)
+        print(exc.output.decode('utf-8'))
         sys.exit(exc.returncode)
     else:
-        print(output, end='')
+        print(output.decode('utf-8'), end='')
 
 
 def _tabulate(output, headers, fmt):

releasenotes/notes/issue-43-c2c166e1fa23fe76.yaml

@@ -0,0 +1,5 @@
+---
+fixes:
+  - |
+    An issue that resulted in invalid output on Python 3 when a patch or series
+    was not successfully applied has been resolved.