Don't use random.choices (new with python 3.6)

Poor Debian users.

api/models.py

@@ -5,6 +5,7 @@ import hashlib
 import random
 import string
 
+
 class ApiKey(models.Model):
     ''' An API key, to login using the API
 
@@ -32,7 +33,8 @@ class ApiKey(models.Model):
         if not self.key:
             KEY_SIZE = 64
             KEY_CHARS = string.ascii_letters + string.digits
-            self.key = ''.join(random.choices(KEY_CHARS, k=KEY_SIZE))
+            self.key = ''.join(
+                [random.choice(KEY_CHARS) for _ in range(KEY_SIZE)])
 
     @property
     def keyId(self):