test: failing doctest in different python version (#320)

* test: issue on test with different python version

* refactor: value error instead of assertion

src/otg/datasource/gwas_catalog/summary_statistics.py

@@ -18,7 +18,7 @@
 
 
 def filename_to_study_identifier(path: str) -> str:
-    r"""Extract GWAS Catalog study identifier from path.
+    """Extract GWAS Catalog study identifier from path.
 
     There's an expectation that the filename has to have the GCST accession of the study.
 
@@ -28,20 +28,24 @@ def filename_to_study_identifier(path: str) -> str:
     Returns:
         str: GWAS Catalog stuy accession.
 
+    Raises:
+        ValueError: If the path does not contain the GWAS Catalog study identifier.
+
     Examples:
         >>> filename_to_study_identifier("http://ftp.ebi.ac.uk/pub/databases/gwas/summary_statistics/GCST006001-GCST007000/GCST006090/harmonised/29895819-GCST006090-HP_0000975.h.tsv.gz")
         'GCST006090'
         >>> filename_to_study_identifier("wrong/path")
         Traceback (most recent call last):
-        ...
-        AssertionError: Path ("wrong/path") does not contain GWAS Catalog study identifier.
+            ...
+        ValueError: Path ("wrong/path") does not contain GWAS Catalog study identifier.
     """
     file_name = path.split("/")[-1]
     study_id_matches = re.search(r"(GCST\d+)", file_name)
 
-    assert (
-        study_id_matches is not None
-    ), f'Path ("{path}") does not contain GWAS Catalog study identifier.'
+    if not study_id_matches:
+        raise ValueError(
+            f'Path ("{path}") does not contain GWAS Catalog study identifier.'
+        )
 
     return study_id_matches[0]