Fix get_request_data compat method

This fixes compat method introduced for #139

The problem lied with how `hasattr` was used.
`hasattr` returned false if `getattr(o, n)`
raises an exception.

Author: jpadilla

rest_framework_jwt/compat.py

@@ -53,9 +53,10 @@ def get_username(user):
 
 
 def get_request_data(request):
-    if hasattr(request, 'data'):
+    if getattr(request, 'data', None):
         data = request.data
     else:
         # DRF < 3.2
         data = request.DATA
+
     return data

tests/test_compat.py

@@ -0,0 +1,28 @@
+import pytest
+from django.test import TestCase
+from rest_framework.request import Request
+from rest_framework.test import APIRequestFactory
+from rest_framework.parsers import JSONParser
+from rest_framework.exceptions import ParseError
+
+from rest_framework_jwt.compat import get_request_data
+
+
+class CompatTests(TestCase):
+    def setUp(self):
+        self.factory = APIRequestFactory()
+
+    def test_get_request_data(self):
+        data = '{"a":"b"}'
+        post = self.factory.post('/', data, content_type='application/json')
+        request = Request(post, parsers=[JSONParser()])
+
+        assert get_request_data(request) == {'a': 'b'}
+
+    def test_get_request_data_invalid(self):
+        data = '{a:b}'
+        post = self.factory.post('/', data, content_type='application/json')
+        request = Request(post, parsers=[JSONParser()])
+
+        with pytest.raises(ParseError):
+            get_request_data(request)