certificate sign with a non-existing cert should throw HTTP 400

Add throw exception for the validate code of CSR. Then it
 will throw HTTP 400 when the CSR validation is not passed.

Change-Id: I6603a2a243097687fef8666343b993c0a18946a9
Closes-Bug: #1543643

magnum/tests/functional/api/v1/test_bay.py

@@ -202,8 +202,8 @@ class BayTest(base.BaseMagnumTest):
 
         # test ca sign invalid
         model = datagen.cert_data(bay_uuid=bay_model.uuid,
-                                  csr_data="invalid_path")
+                                  csr_data="invalid_csr")
         self.assertRaises(
-            exceptions.ServerFault,
+            exceptions.BadRequest,
             self.cert_client.post_cert,
             model)

magnum/tests/functional/common/datagen.py

@@ -295,6 +295,8 @@ def cert_data(bay_uuid, csr_data=None):
     if csr_data is not None and os.path.isfile(csr_data):
         with open(csr_data, 'r') as f:
             data['csr'] = f.read()
+    else:
+        data['csr'] = csr_data
 
     model = cert_model.CertEntity.from_dict(data)