Test partial correlations endpoint with non-existent primary traits

Test that the partial correlations endpoint responds with an appropriate
"not-found" message and the corresponding 404 status code in the case where a
request is made and the primary trait requested for does not exist in the
database.

Summary of the changes in each file:
* gn3/api/correlation.py: generalise the building of the response
* gn3/computations/partial_correlations.py: return with a "not-found" if the
  primary trait does not exist in the database
* gn3/db/partial_correlations.py: Fix a number of bugs that led to exceptions
  in the case that the primary trait did not exist
* pytest.ini: register a `slow` pytest marker
* tests/integration/test_partial_correlations.py: Add a new test to check for
  an appropriate 404 response in case of a primary trait that does not exist
  in the database.

1 files changed, 5 insertions, 0 deletions

diff --git a/gn3/computations/partial_correlations.py b/gn3/computations/partial_correlations.py
index 85e3c11..16cbbdb 100644
--- a/gn3/computations/partial_correlations.py
+++ b/gn3/computations/partial_correlations.py
@@ -616,6 +616,11 @@ def partial_correlations_entry(# pylint: disable=[R0913, R0914, R0911]
     primary_trait = tuple(
         trait for trait in all_traits
         if trait["trait_fullname"] == primary_trait_name)[0]
+    if not primary_trait["haveinfo"]:
+        return {
+            "status": "not-found",
+            "message": f"Could not find primary trait {primary_trait['trait_fullname']}"
+        }
     group = primary_trait["db"]["group"]
     primary_trait_data = all_traits_data[primary_trait["trait_name"]]
     primary_samples, primary_values, _primary_variances = export_informative(