Send pure plain-text mails as quoted-printable

We were already using QP for HTML emails, but due to an oversight it
wasn't done for the pure plaintext ones. Fix that as it's a lot easier
to debug that way, and it's what most MUAs do so it should lead to lower
spam scores.

Author: mhagander

pgweb/mailqueue/util.py

@@ -53,7 +53,7 @@ def send_simple_mail(sender, receiver, subject, msgtxt, attachments=None, userge
             mpart.attach(MIMEText(htmlbody, 'html', _charset=_utf8_charset))
     else:
         # Just a plaintext body, so append it directly
-        mpart = MIMEText(msgtxt, _charset='utf-8')
+        mpart = MIMEText(msgtxt, _charset=_utf8_charset)
 
     if attachments:
         msg = MIMEMultipart()