Remove cyclic dependency from MarkKeyParser.

Rather than calling modeman.leave directly, modeman hooks into a request_leave
signal that is fired when MarkKeyParser wants to exit mark mode.

qutebrowser/keyinput/basekeyparser.py

@@ -67,9 +67,13 @@ class BaseKeyParser(QObject):
     Signals:
         keystring_updated: Emitted when the keystring is updated.
                            arg: New keystring.
+        request_leave: Emitted to request leaving a mode.
+                       arg 0: Mode to leave.
+                       arg 1: Reason for leaving.
     """
 
     keystring_updated = pyqtSignal(str)
+    request_leave = pyqtSignal(usertypes.KeyMode, str)
     do_log = True
     passthrough = False
 

qutebrowser/keyinput/modeman.py

@@ -225,6 +225,7 @@ class ModeManager(QObject):
         assert isinstance(mode, usertypes.KeyMode)
         assert parser is not None
         self._parsers[mode] = parser
+        parser.request_leave.connect(self.leave)
 
     def enter(self, mode, reason=None, only_if_normal=False):
         """Enter a new mode.

qutebrowser/keyinput/modeparsers.py

@@ -27,7 +27,7 @@ from PyQt5.QtCore import pyqtSlot, Qt
 
 from qutebrowser.utils import message
 from qutebrowser.config import config
-from qutebrowser.keyinput import keyparser, modeman
+from qutebrowser.keyinput import keyparser
 from qutebrowser.utils import usertypes, log, objreg, utils
 
 
@@ -276,6 +276,6 @@ class MarkKeyParser(keyparser.BaseKeyParser):
         else:
             raise ValueError("{} is not a valid mark mode".format(self._mode))
 
-        modeman.leave(self._win_id, self._mode, "valid mark key")
+        self.request_leave.emit(self._mode, "valid mark key")
 
         return True