Display Condition Error: Error in calculation for /data/district_name Logic references required which is not a valid question or value. You may have forgotten to include the full path to the question (e.g. /data/required). (Expanded reference: /data/district_name[1]/required)
That error message makes it sound like you wrote the word "required" in the Display Condition box. To make a question required, check the "Required" checkbox:
If you want to control whether or not a question will appear, you can read more about display conditions here:
https://confluence.dimagi.com/display/commcarepublic/Display+Conditions+Overview