Improve random number generator by using a better PRNG function provi…

…ded by the os; fix tests sometimes failing

README.md

@@ -144,7 +144,7 @@ If you want to test this locally, I recommend using some kind of fake mailserver
 
 By default, `email` lookup is used to find the user instance. You can change that by adding 
 ```python
-DJANGO_REST_LOOKUP_FIELD = ''
+DJANGO_REST_LOOKUP_FIELD = 'custom_email_field'
 ```
 into Django settings.py file.
 
@@ -183,6 +183,8 @@ DJANGO_REST_PASSWORDRESET_TOKEN_CONFIG = {
     }
 }
 ```
+
+It uses `os.urandom()` to generate a good random string.
 
 
 ### RandomNumberTokenGenerator
@@ -203,6 +205,8 @@ DJANGO_REST_PASSWORDRESET_TOKEN_CONFIG = {
 }
 ```
 
+It uses `random.SystemRandom().randint()` to generate a good random number.
+
 
 ### Write your own Token Generator
 

django_rest_passwordreset/tokens.py

@@ -71,12 +71,14 @@ def generate_token(self, *args, **kwargs):
 
 class RandomNumberTokenGenerator(BaseTokenGenerator):
     """
-    Generates a random number
+    Generates a random number using random.SystemRandom() (which uses urandom in the background)
     """
     def __init__(self, min_number=10000, max_number=99999, *args, **kwargs):
         self.min_number = min_number
         self.max_number = max_number
 
     def generate_token(self, *args, **kwargs):
+        r = random.SystemRandom()
+
         # generate a random number between min_number and max_number
-        return str(random.randint(self.min_number, self.max_number))
+        return str(r.randint(self.min_number, self.max_number))

tests/test/test_token_generators.py

@@ -41,7 +41,7 @@ def test_string_token_generator(self):
             )
 
     def test_number_token_generator(self):
-        token_generator = RandomNumberTokenGenerator(min_number=100000, max_number=999999)
+        token_generator = RandomNumberTokenGenerator(min_number=1000000000, max_number=9999999999)
 
         tokens = []
 
@@ -72,10 +72,8 @@ def test_number_token_generator(self):
             self.assertEquals(is_number, True, msg="RandomNumberTokenGenerator must return a number, but returned "
                                                    + token)
 
-            self.assertGreaterEqual(num, 100000, msg="RandomNumberTokenGenerator must return a number greater or "
-                                                     "equal to 1000")
-
-            self.assertLess(num, 999999, msg="RandomNumberTokenGenerator must return a number less or equal to 9999")
+            self.assertGreaterEqual(num, 1000000000, msg="RandomNumberTokenGenerator must return a number greater or equal to 1000000000")
+            self.assertLess(num, 9999999999, msg="RandomNumberTokenGenerator must return a number less or equal to 9999999999")
 
     def test_generate_token_generator_from_empty_settings(self):
         """