Cassandra sub-cli has hard dependency on DCOS_CONFIG ENV Variable

[tkrausjr]

Cassandra package sub-cli seems to be misconfigured. Has a hard requirement for DCOS_CONFIG ENV variable to be set. I thought these dependencies were removed. Fix would be to force user to set the variable to dcos.toml file or update: "/Users/tkraus/.dcos/subcommands/cassandra/env/lib/python2.7/site-packages/dcos/util.py" to remove the requirement.

$ dcos cassandra node list --json cassandra.dcos
Traceback (most recent call last): File "/Users/tkraus/.dcos/subcommands/cassandra/env/bin/dcos-cassandra", line 9, in load_entry_point('dcoscassandra===SNAPSHOT', 'console_scripts', 'dcos-cassandra')() File "/Users/tkraus/.dcos/subcommands/cassandra/env/lib/python2.7/site-packages/dcoscassandra/cli.py", line 47, in main return _main() File "/Users/tkraus/.dcos/subcommands/cassandra/env/lib/python2.7/site-packages/dcoscassandra/cli.py", line 63, in _main return cmds.execute(_cmds(), args) File "/Users/tkraus/.dcos/subcommands/cassandra/env/lib/python2.7/site-packages/dcos/cmds.py", line 43, in execute return function(*params) File "/Users/tkraus/.dcos/subcommands/cassandra/env/lib/python2.7/site-packages/dcoscassandra/cli.py", line 208, in _node_list client = cassandra.create_client(service_name) File "/Users/tkraus/.dcos/subcommands/cassandra/env/lib/python2.7/site-packages/dcoscassandra/cassandra.py", line 21, in create_client config = util.get_config() File "/Users/tkraus/.dcos/subcommands/cassandra/env/lib/python2.7/site-packages/dcos/util.py", line 115, in get_config os.environ[constants.DCOS_CONFIG_ENV]) File "/Users/tkraus/.dcos/subcommands/cassandra/env/bin/../lib/python2.7/UserDict.py", line 23, in getitem raise KeyError(key) KeyError: 'DCOS_CONFIG'