Description of problem:


Version-Release number of selected component (if applicable):
3.7.0-SNAPSHOT and below


How reproducible:
Always

Steps to Reproduce:
1. make sure your pom.xml doesn't define zanata.transLang property
2. mvn org.zanata:zanata-maven-plugin:3.7.0-SNAPSHOT:glossary-push -Dzanata.glossaryFile=compendium_fr.po -Dzanata.url=http://localhost:8080/zanata/  


Actual results:
NullPointerException

Expected results:
Meaningful error message e.g. "transLang is required when pushing po format glossary"

Additional info:
transLang is not required when pushing csv format glossary.