Specify python version in mce-cli requirement.txt
-avro-python3==1.8.2; python_version == '3.7
+avro-python3==1.8.2; python_version == '3.7'
confluent-kafka==1.1.0; python_version == '3.7'
confluent-kafka[avro]==1.1.0; python_version < '3.7'
