Fix some issues with closing subprocesses

pyqtgraph/multiprocess/__init__.py

@@ -21,4 +21,4 @@ TODO:
 
 from .processes import *
 from .parallelizer import Parallelize, CanceledError
-from .remoteproxy import proxy
+from .remoteproxy import proxy, ClosedError, NoResultError

pyqtgraph/multiprocess/processes.py

@@ -182,7 +182,8 @@ def startEventLoop(name, port, authkey, ppid, debug=False):
             HANDLER.processRequests()  # exception raised when the loop should exit
             time.sleep(0.01)
         except ClosedError:
-            break
+            HANDLER.debugMsg('Exiting server loop.')
+            sys.exit(0)
 
 
 class ForkedProcess(RemoteEventHandler):

pyqtgraph/multiprocess/remoteproxy.py

@@ -419,7 +419,7 @@ class RemoteEventHandler(object):
             if opts is None:
                 opts = {}
             
-            assert callSync in ['off', 'sync', 'async'], 'callSync must be one of "off", "sync", or "async"'
+            assert callSync in ['off', 'sync', 'async'], 'callSync must be one of "off", "sync", or "async" (got %r)' % callSync
             if reqId is None:
                 if callSync != 'off': ## requested return value; use the next available request ID
                     reqId = self.nextRequestId
@@ -572,6 +572,10 @@ class RemoteEventHandler(object):
             self.proxies[ref] = proxy._proxyId
     
     def deleteProxy(self, ref):
+        if self.send is None:
+            # this can happen during shutdown
+            return
+
         with self.proxyLock:
             proxyId = self.proxies.pop(ref)