bitbake: toaster: Add tests to detect if we have missing db migrations

Based on the same test as found in patchwork by Damien Lespiau
https://github.com/dlespiau/patchwork/blob/master/patchwork/tests/test_db.py

(Bitbake rev: 031cb194aaa1b6cc970fed3fa0d0dbd3ebac163f)

Signed-off-by: Michael Wood <michael.g.wood@intel.com>
Signed-off-by: bavery <brian.avery@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bitbake/lib/toaster/tests/db/test_db.py

@@ -0,0 +1,55 @@
+# The MIT License (MIT)
+#
+# Copyright (c) 2016 Damien Lespiau
+#
+# Permission is hereby granted, free of charge, to any person obtaining a copy
+# of this software and associated documentation files (the "Software"), to deal
+# in the Software without restriction, including without limitation the rights
+# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+# copies of the Software, and to permit persons to whom the Software is
+# furnished to do so, subject to the following conditions:
+#
+# The above copyright notice and this permission notice shall be included in
+# all copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+# SOFTWARE.
+
+import sys
+
+try:
+    from StringIO import StringIO
+except ImportError:
+    from io import StringIO
+
+from contextlib import contextmanager
+
+from django.core import management
+from django.test import TestCase
+
+
+@contextmanager
+def capture(command, *args, **kwargs):
+    out, sys.stdout = sys.stdout, StringIO()
+    command(*args, **kwargs)
+    sys.stdout.seek(0)
+    yield sys.stdout.read()
+    sys.stdout = out
+
+
+def makemigrations():
+    management.call_command('makemigrations')
+
+
+class MigrationTest(TestCase):
+
+    def testPendingMigration(self):
+        """Make sure there's no pending migration."""
+
+        with capture(makemigrations) as output:
+            self.assertEqual(output, "No changes detected\n")