Refactor update creation api

This merge request does the following:

• Raise DRF errors rather than returning response to take advantage of the DRF exception handling mechanism
• Create serialisers for PUT request to simplify the code
• Improve validation checks in several places
• Fixes several issues in DRF infrastructure uses
• Fixes JSON fields handling
• Remove routes that do no fully qualify objects
• Implement a custom DRF exception handler that will allow to log errors
• Improve testing
• Improve permission management

beat/web/experiments/api.py

@@ -62,7 +62,7 @@ from ..common.api import (
 from ..common.mixins import CommonContextMixin
 from ..common.exceptions import ShareError
 from ..common.serializers import SharingSerializer
-from ..common.utils import validate_restructuredtext, ensure_html
+from ..common.utils import validate_restructuredtext, ensure_html, py3_cmp
 
 from ..toolchains.models import Toolchain
 
@@ -111,15 +111,6 @@ class ListCreateExperimentsView(ListCreateContributionView):
         def _getStatusLabel(status):
             return [s for s in Experiment.STATUS if s[0] == status][0][1]
 
-        def _cmp(a, b):
-            """
-            cmp is not available anymore in Python 3. This method is implemetend
-            as recommended in the documentation for this kind of use case.
-            Based on:
-              https://docs.python.org/3.0/whatsnew/3.0.html#ordering-comparisons
-            """
-            return (a > b) - (a < b)
-
         def _custom_compare(exp1, exp2):
             PENDING = _getStatusLabel(Experiment.PENDING)
 
@@ -129,7 +120,7 @@ class ListCreateExperimentsView(ListCreateContributionView):
                 if exp2["status"] != PENDING:
                     return -1
                 elif exp1["creation_date"] != exp2["creation_date"]:
-                    return _cmp(exp1["creation_date"], exp2["creation_date"])
+                    return py3_cmp(exp1["creation_date"], exp2["creation_date"])
                 else:
                     return 1
             elif exp2["status"] == PENDING:
@@ -142,7 +133,7 @@ class ListCreateExperimentsView(ListCreateContributionView):
             ]
 
             if (exp1["status"] in tier3_states) and (exp2["status"] in tier3_states):
-                return _cmp(exp2["end_date"], exp1["end_date"])
+                return py3_cmp(exp2["end_date"], exp1["end_date"])
             elif (exp1["status"] in tier3_states) and (
                 exp2["status"] not in tier3_states
             ):
@@ -152,7 +143,7 @@ class ListCreateExperimentsView(ListCreateContributionView):
             ):
                 return 1
 
-            return _cmp(exp1["start_date"], exp2["start_date"])
+            return py3_cmp(exp1["start_date"], exp2["start_date"])
 
         # Retrieve the experiments
         fields_to_return_original = self.get_serializer_fields(request)