Correcting an issue where dbg_output was not defined when the server was

unreachable due to an optimization in PR#56.  Since message-id is more
useful to better pin point the correct message, removing dbg_output.

Also fixing https://github.com/OfflineIMAP/offlineimap3/issues/62 by
correcting broken multipart boundaries or raising an error if as_bytes()
fails.  Related python bug submitted: https://bugs.python.org/issue43818
although this workaround should be sufficent in the interim.

Signed-off-by: Joseph Ishac <jishac@nasa.gov>

offlineimap/folder/Base.py

@@ -26,7 +26,6 @@ from email import policy
 from email.parser import BytesParser
 from email.generator import BytesGenerator
 from email.utils import parsedate_tz, mktime_tz
-from email.errors import NoBoundaryInMultipartDefect
 
 from offlineimap import threadutil
 from offlineimap.ui import getglobalui

offlineimap/folder/Maildir.py

@@ -25,6 +25,7 @@ from threading import Lock
 from hashlib import md5
 from offlineimap import OfflineImapError
 from .Base import BaseFolder
+from email.errors import NoBoundaryInMultipartDefect
 
 # Find the UID in a message filename
 re_uidmatch = re.compile(',U=(\d+)')
@@ -297,24 +298,29 @@ class MaildirFolder(BaseFolder):
         filename = self.messagelist[uid]['filename']
         filepath = os.path.join(self.getfullname(), filename)
         fd = open(filepath, 'rb')
-        retval = self.parser['8bit'].parse(fd)
+        _fd_bytes = fd.read()
-        try:
-            if len(retval.defects) > 0:
-                ui.warn("Message has defects: {}".format(retval.defects))
-                # See if the defects are preventing us from obtaining bytes and
-                # handle known issues
-                _ = retval.as_bytes(policy=self.policy['8bit'])
-        except UnicodeEncodeError as err:
-            if any(isinstance(defect, NoBoundaryInMultipartDefect) for defect in retval.defects):
-                # (Hopefully) Rare instance where multipart boundary is not
-                # properly quoted.  Solve by fixing the boundary and parsing
-                fd.seek(0)
-                _buffer = fd.read()
-                retval = self.parser['8bit'].parsebytes(_quote_boundary_fix(_buffer))
-            else:
-                # Unknown issue which is causing failure of as_bytes()
-                ui.warn("Message has defects preventing it from being processed!")
         fd.close()
+        retval = self.parser['8bit'].parsebytes(_fd_bytes)
+        if len(retval.defects) > 0:
+            # We don't automatically apply fixes as to attempt to preserve the original message
+            self.ui.warn("UID {} has defects: {}".format(uid, retval.defects))
+            if any(isinstance(defect, NoBoundaryInMultipartDefect) for defect in retval.defects):
+                # (Hopefully) Rare defect from a broken client where multipart boundary is
+                # not properly quoted.  Attempt to solve by fixing the boundary and parsing
+                self.ui.warn(" ... applying multipart boundary fix.")
+                retval = self.parser['8bit'].parsebytes(self._quote_boundary_fix(_fd_bytes))
+            try:
+                # See if the defects after fixes are preventing us from obtaining bytes
+                _ = retval.as_bytes(policy=self.policy['8bit'])
+            except UnicodeEncodeError as err:
+                # Unknown issue which is causing failure of as_bytes()
+                msg_id = self.getmessageheader(retval, "message-id")
+                if msg_id is None:
+                    msg_id = '<unknown-message-id>'
+                raise OfflineImapError(
+                        "UID {} ({}) has defects preventing it from being processed!\n  {}: {}".format(
+                            uid, msg_id, type(err).__name__, err),
+                        OfflineImapError.ERROR.MESSAGE)
         return retval
 
     # Interface from BaseFolder