Merge pull request #294 in CASA/casa6 from CAS-13263 to master
* commit 'cbc32563f44a5ff99a53c0d493962e84974d0110':
Fix Merge Conflicts
Fix for ModuleNotFound Error in Python2
Try / except for ModuleNotFoundError in Python2 ( Casa5)
Add missing colon in testhelpers. Remove unused import modules. Fixed typo in np.pi. Sync CASA6 and CASA5 versions of casatestutils
Set install requires to only six, numpy, scipy
Add modules to install_requires
Remove most references to is_casa6 as boolean
Fix for th import for casatools tests
Fixes for ModuleNotFoundError in casatools tests
Update to new setup.py
Check between py2 and py3 for using dict.keys
Add 'six' to dependency list
Replace use of testhelper and other helper files in tests to use casatestutils
Update tests using selection_syntax, listing, filltsys to use versions in casatestutils
