Make BackgroundRectangle stroke_opacity 0

manimlib/mobject/mobject.py

@@ -1107,7 +1107,7 @@ class Mobject(Container):
     # Errors
     def throw_error_if_no_points(self):
         if self.has_no_points():
-            message = "Cannot call Mobject.{}" +\
+            message = "Cannot call Mobject.{} " +\
                       "for a Mobject with no points"
             caller_name = sys._getframe(1).f_code.co_name
             raise Exception(message.format(caller_name))

manimlib/mobject/shape_matchers.py

@@ -25,6 +25,7 @@ class BackgroundRectangle(SurroundingRectangle):
     CONFIG = {
         "color": BLACK,
         "stroke_width": 0,
+        "stroke_opacity": 0,
         "fill_opacity": 0.75,
         "buff": 0
     }