Fix weird test behaviour

The test was modifying a fixture, and this fixture is not in .gitignore.
The consequence is that if there were errors, the fixture was changed and developers would potentially commit an invalid fixture due to this.
This PR leverages the previous change introduced in #236 to use envvars for templating YML filepaths

tests/fixtures/dag_factory.yml

@@ -33,7 +33,7 @@ example_dag:
       - task_1
       operator: airflow.operators.bash_operator.BashOperator
 example_dag2:
-  doc_md_file_path: {here}/fixtures/mydocfile.md
+  doc_md_file_path: $PWD/tests/fixtures/mydocfile.md
   schedule_interval: None
   tasks:
     task_1:
@@ -53,7 +53,7 @@ example_dag3:
   doc_md_python_arguments:
     arg1: arg1
     arg2: arg2
-  doc_md_python_callable_file: {here}/fixtures/doc_md_builder.py
+  doc_md_python_callable_file: $PWD/tests/fixtures/doc_md_builder.py
   doc_md_python_callable_name: mydocmdbuilder
   tasks:
     task_1:

tests/test_dagfactory.py

@@ -91,18 +91,6 @@
 }
 
 
-@pytest.fixture(autouse=True)
-def build_path_for_doc_md():
-    with open(TEST_DAG_FACTORY, "r") as f:
-        oldText = f.read()
-        newText = oldText.replace("{here}", here)
-    with open(TEST_DAG_FACTORY, "w") as f:
-        f.write(newText)
-    yield
-    with open(TEST_DAG_FACTORY, "w") as f:
-        f.write(oldText)
-
-
 def test_validate_config_filepath_valid():
     dagfactory.DagFactory._validate_config_filepath(TEST_DAG_FACTORY)