Fix potential deadlock and delayed notification

The hard limiter was checked before the value was set. That means, if
the user sets a valid outside the hard limit, he will not see an exception
(because we don't know yet if we are in hard limit) nor can he return to a valid
value later on (because we abort before we set anything).

concert/base.py

@@ -225,10 +225,6 @@ def set(self, value, owner=None):
             msg = "`{0}' can only receive values of unit {1} but got {2}"
             raise UnitError(msg.format(self.name, self.unit, value))
 
-        if self.limiter and not self.limiter(value):
-            msg = "{0} for `{1}' is out of range"
-            raise LimitError(msg.format(value, self.name))
-
         def log_access(what):
             """Log access."""
             msg = "{0}: {1} {2}='{3}'"
@@ -242,6 +238,10 @@ def log_access(what):
         else:
             self._fset(value)
 
+            if self.limiter and not self.limiter(value):
+                msg = "{0} for `{1}' is out of range"
+                raise LimitError(msg.format(value, self.name))
+
         log_access('set')
         self.notify()