Fix workarounds for MUAs that don't handle UTF-8

Turns out that clean_header() takes Header, so we were getting:
  AttributeError
  'Header' object has no attribute 'startswith'

Let's use Header in the test and fix the issue properly.

Fix: a7046dca ("Add workaround for MUAs that don't handle UTF-8")
Signed-off-by: Arkadiusz Hiler <arkadiusz.hiler@intel.com>

patchwork/bin/parsemail.py

@@ -79,13 +79,12 @@ def normalise_space(str):
 def clean_header(header):
     """ Decode (possibly non-ascii) headers """
 
-    if header.startswith('=?unknown-8bit?'):
-        LOGGER.debug("unknown-8bit in header, trying to assume utf-8")
-        header = header.replace('=?unknown-8bit?', '=?utf-8?')
-
     def decode(fragment):
         (frag_str, frag_encoding) = fragment
         if frag_encoding:
+            if frag_encoding == 'unknown-8bit':
+                frag_encoding = 'utf-8'
+                LOGGER.debug("unknown-8bit in header, trying to assume utf-8")
             return frag_str.decode(frag_encoding)
         elif isinstance(frag_str, bytes):
             return frag_str.decode()

patchwork/tests/test_patchparser.py

@@ -21,6 +21,7 @@ from email import message_from_string
 from email.mime.text import MIMEText
 from email.utils import make_msgid
 from email.parser import HeaderParser
+from email.header import make_header
 
 from django.test import TestCase, TransactionTestCase
 
@@ -1163,11 +1164,13 @@ class SubjectTest(TestCase):
                          ('[bar] meep', ['bar']))
 
     def testHandlesUTF8(self):
-        h = '=?utf-8?b?4pyXIEZpLkNJLkNIRUNLUEFUQ0g6IHdhcm5pbmcg?='
+        raw_utf8 = '✗ Fi.CI.CHECKPATCH: warning'
+        h = make_header([(raw_utf8.encode(), 'utf-8')])
         h = clean_header(h)
-        self.assertEqual('✗ Fi.CI.CHECKPATCH: warning', h)
+        self.assertEqual(raw_utf8, h)
 
     def testCleanHeaderUnknown8bit(self):
-        h = '=?unknown-8bit?q?=E2=9C=97_Fi=2ECI=2EIGT=3A_failure?='
+        raw_utf8 = '✗ Fi.CI.CHECKPATCH: warning'
+        h = make_header([(raw_utf8.encode(), 'unknown-8bit')])
         h = clean_header(h)
-        self.assertEqual('✗ Fi.CI.IGT: failure', h)
+        self.assertEqual(raw_utf8, h)