Try fixing import error of example.modelchain_example when notebooks are run on github

Author: birgits

example/test_examples.py

@@ -56,7 +56,9 @@ def _notebook_run(self, path):
         Execute a notebook and collect output.
         Returns (parsed nb object, execution errors)
         """
-        notebook = pytest_notebook.notebook.load_notebook(path=path)
+        dirname, nb_name = os.path.split(path)
+        os.chdir(dirname)
+        notebook = pytest_notebook.notebook.load_notebook(path=nb_name)
         result = pytest_notebook.execution.execute_notebook(
             notebook,
             with_coverage=False,