gateway_base: remove Semaphore from execmodel

Not used since 120f639.

Author: bluetech

execnet/gateway_base.py

@@ -29,10 +29,6 @@
 #     f.write(" ".join([str(x) for x in msg]) + "\n")
 
 
-class EmptySemaphore:
-    acquire = release = lambda self: None
-
-
 def get_execmodel(backend):
     if hasattr(backend, "backend"):
         return backend
@@ -117,11 +113,6 @@ def __getattr__(self, name):
         def fdopen(self, fd, mode, bufsize=1):
             return self._fdopen(fd, mode, bufsize)
 
-        def Semaphore(self, size=None):
-            if size is None:
-                return EmptySemaphore()
-            return self._lock.Semaphore(size)
-
         def Lock(self):
             return self._lock.RLock()