[PATCH v2 6/9] REST: Allow for mutability of request.POST

[Stephen Finucane]

Using Django 1.11 yields the following error for the 'patchwork.tests
.test_rest_api.TestCheckAPI.test_create' test:

    AttributeError: This QueryDict instance is immutable

This occurs due to our modification of data to allow users to create
instances using a slugified state instead of the underlying integer
value, e.g. 'success' instead of 1.

Resolve this by unsetting the immutability of that queryset. As
suggested in the linked SO answer, there is limited side effects to
doing this.

Signed-off-by: Stephen Finucane <stephen at that.guru>
---
 patchwork/api/check.py | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/patchwork/api/check.py b/patchwork/api/check.py
index 5b381505..b37d6e01 100644
--- a/patchwork/api/check.py
+++ b/patchwork/api/check.py
@@ -49,7 +49,16 @@ class CheckSerializer(HyperlinkedModelSerializer):
     def run_validation(self, data):
         for val, label in Check.STATE_CHOICES:
             if label == data['state']:
+                # NOTE(stephenfin): 'data' is essentially 'request.POST', which
+                # is immutable by default. However, there's no good reason for
+                # this to be this way [1], so temporarily unset that mutability
+                # to fix what we need to here.
+                #
+                # [1] http://stackoverflow.com/a/12619745/613428
+                mutable = data._mutable  # noqa
+                data._mutable = True  # noqa
                 data['state'] = val
+                data._mutable = mutable  # noqa
                 break
         return super(CheckSerializer, self).run_validation(data)
 
-- 
2.13.6