Fixes an error occurring when editing a User as Developer when the ToS have been signed.
By disabling the input of the field Django will not attempt to wrongly parse it as a DateTime instance.
Patch by: Haoyu Bai
Reviewed by: Lennard de Rijk
Coverage: code coverage testing for Python
Coverage.py is a Python module that measures code coverage during test execution.
It uses the code analysis tools and tracing hooks provided in the Python standard
library to determine which lines are executable, and which have been executed.
For more information, see http://nedbatchelder.com/code/modules/coverage.html