Fixed test_environment_vars_in_config_file

Some small changes to get this test to work. Unfortunately
diffenigne.config is a global in the diffengine module, and
changing it doesn't play nicely with the tests. I added a
return value for diffengine.load_config that makes this easier.

refs #67

.gitignore

@@ -11,3 +11,4 @@ diffengine.egg-info
 build
 Pip*
 .venv
+.env

diffengine/__init__.py

@@ -367,6 +367,7 @@ def load_config(prompt=True):
         if prompt:
             config = get_initial_config()
         yaml.dump(config, open(config_file, "w"), default_flow_style=False)
+    return config
 
 def get_initial_config():
     config = {"feeds": []}

test_diffengine.py

@@ -135,13 +135,12 @@ def test_environment_vars_in_config_file():
             "public_value": public_value
         }
     }
-    config_file = home_path(test_home, "config.yaml");
+    config_file = home_path("config.yaml");
     yaml.dump(test_config, open(config_file, "w"), default_flow_style=False)
 
     # Test!
-    init("test")
-    config = get_initial_config()
-    assert config['example']['public_value'] == public_value
-    assert config['example']['private_value'] != private_yaml_key
-    assert config['example']['private_value'] == private_value
+    new_config = load_config()
+    assert new_config['example']['public_value'] == public_value
+    assert new_config['example']['private_value'] != private_yaml_key
+    assert new_config['example']['private_value'] == private_value