Update BaseClasses.py

This is how it already works for locations and it feels more correct to me to check in the place where the crash would happen.

Also update location error to be a bit more verbose

BaseClasses.py

@@ -720,7 +720,7 @@ class CollectionState():
             if new_region in reachable_regions:
                 blocked_connections.remove(connection)
             elif connection.can_reach(self):
-                assert new_region, f"tried to search through an Entrance \"{connection}\" with no Region"
+                assert new_region, f"tried to search through an Entrance \"{connection}\" with no connected Region"
                 reachable_regions.add(new_region)
                 blocked_connections.remove(connection)
                 blocked_connections.update(new_region.exits)
@@ -946,6 +946,7 @@ class Entrance:
         self.player = player
 
     def can_reach(self, state: CollectionState) -> bool:
+        assert self.parent_region, f"called can_reach on an Entrance \"{self}\" with no parent_region"
         if self.parent_region.can_reach(state) and self.access_rule(state):
             if not self.hide_path and not self in state.path:
                 state.path[self] = (self.name, state.path.get(self.parent_region, (self.parent_region.name, None)))
@@ -1166,7 +1167,7 @@ class Location:
 
     def can_reach(self, state: CollectionState) -> bool:
         # Region.can_reach is just a cache lookup, so placing it first for faster abort on average
-        assert self.parent_region, "Can't reach location without region"
+        assert self.parent_region, f"called can_reach on a Location \"{self}\" with no parent_region"
         return self.parent_region.can_reach(state) and self.access_rule(state)
 
     def place_locked_item(self, item: Item):