Improve error message for packages missing dbt_project.yml (#6685)

* Improve error message for packages missing `dbt_project.yml`

* Use black formatting

* Update capitalization of expected error message

.changes/unreleased/Features-20230120-112921.yaml

@@ -0,0 +1,6 @@
+kind: Features
+body: Improve error message for packages missing `dbt_project.yml`
+time: 2023-01-20T11:29:21.509967-07:00
+custom:
+  Author: dbeatty10
+  Issue: "6663"

core/dbt/config/project.py

@@ -75,6 +75,11 @@
 {error}
 """
 
+MISSING_DBT_PROJECT_ERROR = """\
+No dbt_project.yml found at expected path {path}
+Verify that each entry within packages.yml (and their transitive dependencies) contains a file named dbt_project.yml
+"""
+
 
 @runtime_checkable
 class IsFQNResource(Protocol):
@@ -163,9 +168,7 @@ def _raw_project_from(project_root: str) -> Dict[str, Any]:
 
     # get the project.yml contents
     if not path_exists(project_yaml_filepath):
-        raise DbtProjectError(
-            "no dbt_project.yml found at expected path {}".format(project_yaml_filepath)
-        )
+        raise DbtProjectError(MISSING_DBT_PROJECT_ERROR.format(path=project_yaml_filepath))
 
     project_dict = _load_yaml(project_yaml_filepath)
 

test/unit/test_config.py

@@ -798,7 +798,7 @@ def test_no_project(self):
         with self.assertRaises(dbt.exceptions.DbtProjectError) as exc:
             dbt.config.Project.from_project_root(self.project_dir, renderer)
 
-        self.assertIn('no dbt_project.yml', str(exc.exception))
+        self.assertIn('No dbt_project.yml', str(exc.exception))
 
     def test_invalid_version(self):
         self.default_project_data['require-dbt-version'] = 'hello!'