If synclabels is enabled then offlineimap is sending '1:*' to imaplib2,
and imaplib2 while creating the FETCH command is quoting the sequence
and the command becomes:
b"JFFJ10 FETCH '1:*' (FLAGS X-GM-LABELS UID)\r\n"
Remove the single-quotes to prevent that and also consider the response
as bytes.
Closes: #52
Signed-off-by: Sudip Mukherjee <sudipm.mukherjee@gmail.com>