fix tox -e mypy tests

Author: mrnicegyu11

mypy.ini

@@ -17,4 +17,6 @@
   strict_equality = True
   strict_optional = True
   no_implicit_optional =  True
-  no_implicit_reexport = True
+  no_implicit_reexport = True
+  # https://mypy.readthedocs.io/en/stable/running_mypy.html#follow-imports
+  follow_imports = silent

opentelemetry-api/tests/context/base_context.py

@@ -64,7 +64,7 @@ def test_attach(self):
             self.assertEqual("yyy", context.get_value("a"))
 
             with self.assertLogs(level=ERROR):
-                context.detach("some garbage")
+                context.detach(token)
 
         def test_detach_out_of_order(self):
             t1 = context.attach(context.set_value("c", 1))