Fix error handling merge pr not found

src/git_portfolio/github_service.py

@@ -255,7 +255,7 @@ def merge_pull_request_from_repo(
         head = f"{pr_merge.prefix}:{pr_merge.head}"
         pulls = list(repo.pull_requests(base=pr_merge.base, head=head))
         if not pulls:
-            return (
+            raise GithubServiceError(
                 f"{github_repo}: no open PR found for "
                 f"{pr_merge.base}:{pr_merge.head}.\n"
             )

tests/test_github_service.py

@@ -797,11 +797,13 @@ def test_merge_pull_request_from_repo_not_found(
     """It gives error message."""
     repo = mock_github3_login.return_value.repositories.return_value[1]
     repo.pull_requests.return_value = []
-    response = gs.GithubService(
-        domain_gh_conn_settings[0]
-    ).merge_pull_request_from_repo(REPO, domain_mpr)
 
-    assert response == f"{REPO}: no open PR found for branch:main.\n"
+    with pytest.raises(
+        gs.GithubServiceError, match=f"{REPO}: no open PR found for branch:main.\n"
+    ):
+        gs.GithubService(domain_gh_conn_settings[0]).merge_pull_request_from_repo(
+            REPO, domain_mpr
+        )
 
 
 def test_merge_pull_request_from_repo_ambiguous(