apache-airflow: correctly run pytest checks

Previously the whole checkPhase was overridden with the preparatory test setup
commands, which prevented pytestCheckHook from having an effect. Fixed to do the
preparatory work in preCheck.

pkgs/development/python-modules/apache-airflow/default.nix

@@ -238,12 +238,17 @@ buildPythonPackage rec {
     "--prefix PYTHONPATH : $PYTHONPATH"
   ];
 
+  postInstall = ''
+    cp -rv ${airflow-frontend}/static/dist $out/lib/${python.libPrefix}/site-packages/airflow/www/static
+    # Needed for pythonImportsCheck below
+    export HOME=$(mktemp -d)
+  '';
+
   pythonImportsCheck = [
     "airflow"
   ] ++ providerImports;
 
-  checkPhase = ''
-    export HOME=$(mktemp -d)
+  preCheck = ''
     export AIRFLOW_HOME=$HOME
     export AIRFLOW__CORE__UNIT_TEST_MODE=True
     export AIRFLOW_DB="$HOME/airflow.db"
@@ -262,10 +267,6 @@ buildPythonPackage rec {
     "bash_operator_kill" # psutil.AccessDenied
   ];
 
-  postInstall = ''
-    cp -rv ${airflow-frontend}/static/dist $out/lib/${python.libPrefix}/site-packages/airflow/www/static
-  '';
-
   # Updates yarn.lock and package.json
   passthru.updateScript = writeScript "update.sh" ''
     #!/usr/bin/env nix-shell