Move stray magic values to literals.py in the checkout app. gh-issue #225.

mayan/apps/checkouts/literals.py

@@ -2,6 +2,9 @@ from __future__ import unicode_literals
 
 from django.utils.translation import ugettext_lazy as _
 
+CHECK_EXPIRED_CHECK_OUTS_INTERVAL = 60  # Lowest check out expiration allowed
+CHECKOUT_EXPIRATION_LOCK_EXPIRE = 50
+
 STATE_CHECKED_OUT = 'checkedout'
 STATE_CHECKED_IN = 'checkedin'
 
@@ -9,3 +12,4 @@ STATE_LABELS = {
     STATE_CHECKED_OUT: _('Checked out'),
     STATE_CHECKED_IN: _('Checked in/available'),
 }
+