Add exception for method calls outside of module instance

Author: dylanjw

tests/core/method-class/test_method.py

@@ -270,7 +270,7 @@ def dummy_w3():
 
 
 def test_munger_class_method_access_raises_friendly_error():
-    with pytest.raises(Exception):
+    with pytest.raises(TypeError):
         FakeModule.method(1, 2)
 
 

web3/method.py

@@ -83,6 +83,11 @@ def __init__(
         self.formatter_lookup_fn = formatter_lookup_fn or get_default_formatters
 
     def __get__(self, obj=None, obj_type=None):
+        if obj is None:
+            raise TypeError(
+                "Direct calls to methods are not supported. "
+                "Methods must be called from an module instance, "
+                "usually attached to a web3 instance.")
         return obj.retrieve_caller_fn(self)
 
     @property