yum-cron: don't crash with non-ascii email. BZ 1202680

Previously, we constructed our MIMEText object with the default us-ascii
charset, which caused it to encode the unicode string (self.output) with
the us-ascii codec.  This worked fine as long as the string contained
ascii-only chars.  However, if yum-cron was run with a language which
makes use of non-ascii chars, this would fail and MIMEText would crash.

To fix that, we need to tell MIMEText to encode the message with utf-8
instead.  However, that also causes the message to be transfer-encoded
to base64 which is heavier and uglier, so let's limit that to non-ascii
email only.

yum-cron/yum-cron.py

@@ -223,8 +223,18 @@ def sendMessages(self):
  # Don't send empty emails
  if not self.output:
  return
- # Build up the email to be sent
- msg = MIMEText(''.join(self.output))
+ # Build up the email to be sent. Encode it with us-ascii instead of
+ # utf-8 if possible. This ensures the email package will not
+ # transfer-encode it to base64 in such a case (it decides based on the
+ # charset passed to the MIMEText constructor).
+ output = ''.join(self.output)
+ try:
+ output.encode('us-ascii')
+ except UnicodeEncodeError:
+ charset = 'utf-8'
+ else:
+ charset = 'us-ascii'
+ msg = MIMEText(output, 'plain', charset)
  msg['Subject'] = self.subject
  msg['From'] = self.opts.email_from
  msg['To'] = ",".join(self.opts.email_to)