composer: Set up a custom HTTP error handler

Override flask's default error handler, because that return html. Return
JSON instead with the usual { "status": false, "errors": [ ... ] }
pattern.

src/pylorax/api/errors.py

@@ -16,6 +16,9 @@
 # You should have received a copy of the GNU General Public License
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
+# HTTP errors
+HTTP_ERROR = "HTTPError"
+
 # Returned from the API when either an invalid compose type is given, or not
 # compose type is given.
 BAD_COMPOSE_TYPE = "BadComposeType"

src/pylorax/api/server.py

@@ -21,9 +21,11 @@ from collections import namedtuple
 from flask import Flask, jsonify, redirect, send_from_directory
 from glob import glob
 import os
+import werkzeug
 
 from pylorax import vernum
 from pylorax.api.crossdomain import crossdomain
+from pylorax.api.errors import HTTP_ERROR
 from pylorax.api.v0 import v0_api
 from pylorax.sysutils import joinpaths
 
@@ -79,4 +81,8 @@ def v0_status():
                    db_supported=True,
                    msgs=server.config["TEMPLATE_ERRORS"])
 
+@server.errorhandler(werkzeug.exceptions.HTTPException)
+def bad_request(error):
+    return jsonify(status=False, errors=[{ "id": HTTP_ERROR, "code": error.code, "msg": error.name }]), error.code
+
 v0_api(server)

tests/pylorax/test_server.py

@@ -1553,6 +1553,26 @@ class ServerTestCase(unittest.TestCase):
         self.assertTrue(len(data["errors"]) > 0)
         self.assertEqual(data["errors"][0]["id"], "UnknownBlueprint")
 
+    def test_404(self):
+        """Test that a 404 returns JSON"""
+        resp = self.server.get("/marmalade")
+        print(resp)
+        print(resp.data)
+        self.assertEqual(resp.status_code, 404)
+        self.assertEqual(json.loads(resp.data), {
+            "status": False,
+            "errors": [{ "id": "HTTPError", "code": 404, "msg": "Not Found" }]
+        })
+
+    def test_405(self):
+        """Test that a 405 returns JSON"""
+        resp = self.server.post("/api/status")
+        self.assertEqual(resp.status_code, 405)
+        self.assertEqual(json.loads(resp.data), {
+            "status": False,
+            "errors": [{ "id": "HTTPError", "code": 405, "msg": "Method Not Allowed" }]
+        })
+
 @contextmanager
 def in_tempdir(prefix='tmp'):
     """Execute a block of code with chdir in a temporary location"""