BUG: Right format for password from remotepassfile

Reading the password using remotepassfile returns a bytes objects
instead an utf-8 string.

This patch includes support strings and bytes objects.

Closes: #40

Signed-off-by: Sudip Mukherjee <sudipm.mukherjee@gmail.com>

offlineimap/repository/IMAP.py

@@ -590,7 +590,20 @@ class IMAPRepository(BaseRepository):
                              encoding='utf-8')
             password = file_desc.readline().strip()
             file_desc.close()
-            return password.encode('UTF-8')
+
+            # We need a str password
+            if isinstance(password, bytes):
+                return password.decode(encoding='utf-8')
+            elif isinstance(password, str):
+                return password
+
+            # If is not bytes or str, we have a problem
+            raise OfflineImapError("Could not get a right password format for"
+                                   " repository %s. Type found: %s. "
+                                   "Please, open a bug." %
+                                   (self.name, type(password)),
+                                   OfflineImapError.ERROR.FOLDER)
+
         # 4. Read password from ~/.netrc.
         try:
             netrcentry = netrc.netrc().authenticators(self.gethost())