Fix filepath in optional_imports test

Author: marthacryan

tests/test_core/test_optional_imports/test_optional_imports.py

@@ -24,7 +24,7 @@ def test_get_module_does_not_exist(self):
 
     def test_get_module_import_exception(self):
         # Get module that raises an exception on import
-        module_str = "plotly.tests.test_core." "test_optional_imports.exploding_module"
+        module_str = ("tests.test_core.test_optional_imports.exploding_module")
 
         if sys.version_info >= (3, 4):
             with self.assertLogs("_plotly_utils.optional_imports", level="ERROR") as cm:
@@ -38,7 +38,6 @@ def test_get_module_import_exception(self):
                 "ERROR:_plotly_utils.optional_imports:"
                 "Error importing optional module " + module_str
             )
-
             self.assertEqual(cm.output[0][: len(expected_start)], expected_start)
 
             # Check that exception message is included after log message