Surface an error to the user when no base module could be found in the module's buildrequires

module_build_service/utils/mse.py

@@ -251,8 +251,10 @@ def get_mmds_required_by_module_recursively(
     # Get the MMDs of all compatible base modules based on the buildrequires.
     base_module_mmds = _get_base_module_mmds(mmd)
     if not base_module_mmds:
-        raise ValueError("No base module found in buildrequires section of %s" % ":".join(
-            [mmd.get_name(), mmd.get_stream(), str(mmd.get_version())]))
+        base_module_choices = ' or '.join(conf.base_module_names)
+        raise UnprocessableEntity(
+            "None of the base module ({}) streams in the buildrequires section could be found"
+            .format(base_module_choices))
 
     # Add base modules to `mmds`.
     for base_module in base_module_mmds:

tests/staged_data/testmodule-no-base-module.yaml

@@ -0,0 +1,38 @@
+document: modulemd
+version: 2
+data:
+  summary: A test module in all its beautiful beauty
+  description: >-
+    This module demonstrates how to write simple modulemd files And can be used for
+    testing the build and release pipeline.
+  license:
+    module:
+    - MIT
+  dependencies:
+  - buildrequires:
+      platform: [Go]
+    requires:
+      platform: [Sox]
+  references:
+    community: https://docs.pagure.org/modularity/
+    documentation: https://fedoraproject.org/wiki/Fedora_Packaging_Guidelines_for_Modules
+  profiles:
+    default:
+      rpms:
+      - tangerine
+  api:
+    rpms:
+    - perl-Tangerine
+    - tangerine
+  components:
+    rpms:
+      perl-List-Compare:
+        rationale: A dependency of tangerine.
+        ref: master
+      perl-Tangerine:
+        rationale: Provides API for this module and is a dependency of tangerine.
+        ref: master
+      tangerine:
+        rationale: Provides API for this module.
+        ref: master
+        buildorder: 10

tests/test_views/test_views.py

@@ -800,6 +800,23 @@ class TestViews:
         assert module.buildrequires[0].context == '00000000'
         assert module.buildrequires[0].stream_version == 280000
 
+    @patch('module_build_service.auth.get_user', return_value=user)
+    @patch('module_build_service.scm.SCM')
+    def test_submit_build_no_base_module(self, mocked_scm, mocked_get_user):
+        FakeSCM(mocked_scm, 'testmodule', 'testmodule-no-base-module.yaml',
+                '620ec77321b2ea7b0d67d82992dda3e1d67055b4')
+
+        rv = self.client.post('/module-build-service/2/module-builds/', data=json.dumps(
+            {'branch': 'master', 'scmurl': 'git://pkgs.stg.fedoraproject.org/modules/'
+                'testmodule.git?#68931c90de214d9d13feefbd35246a81b6cb8d49'}))
+        data = json.loads(rv.data)
+        assert data == {
+            'status': 422,
+            'message': ('None of the base module (platform) streams in the buildrequires section '
+                        'could be found'),
+            'error': 'Unprocessable Entity'
+        }
+
     @patch('module_build_service.auth.get_user', return_value=user)
     @patch('module_build_service.scm.SCM')
     @patch('module_build_service.config.Config.rebuild_strategy_allow_override',