PyQt: QMutexLocker not released on exception
def query(self,query):
  lock = QMutexLocker(self.mutex)
  reply = self.conn.query(query)
  if (re.search("error", reply) != None):
    raise GeneralError("Query error")

  #more code...
  return reply

def query(self, query):
    lock = QMutexLocker(self.mutex)
    reply = self.conn.query(query)
    if re.search("error", reply):
        lock.unlock()
        raise GeneralError("Query error")

from PyQt4.QtCore import QMutex, QMutexLocker

def bad_lock(aLock):
    locker = QMutexLocker(aLock)
    print "Locked"
    raise RuntimeError("Test exception")

    return "Should not get here"

def good_lock(aLock):
    with QMutexLocker(aLock):
        print "Locked"
        raise RuntimeError("Test exception")

    return "Should not get here"

lock = QMutex()

bad_lock(lock)
print lock.tryLock()
# False

lock.unlock()

good_lock(lock)
print lock.tryLock()
# True

def good_lock(aLock):

    # do a bunch of stuff here
    ...

    # critical section
    with QMutexLocker(aLock):
        # do critical stuff here
        ...

    # do other stuff here
    ...

    return True