Fstab.remove_entry() will crash if the current fstab file contains any blank lines or comments. It needs to guard access to _hydrate_entry, similar to how the Fstab.entries property does it.
unit-cassandra-0[17198]: 2015-02-17 18:55:26 INFO unit.cassandra/0.install logger.go:40 File "/var/lib/juju/agents/unit-cassandra-0/charm/hooks/actions.py", line 99, in wrapper
unit-cassandra-0[17198]: 2015-02-17 18:55:26 INFO unit.cassandra/0.install logger.go:40 return func(*args, **kw)
unit-cassandra-0[17198]: 2015-02-17 18:55:26 INFO unit.cassandra/0.install logger.go:40 File "/var/lib/juju/agents/unit-cassandra-0/charm/hooks/actions.py", line 172, in swapoff
unit-cassandra-0[17198]: 2015-02-17 18:55:26 INFO unit.cassandra/0.install logger.go:40 fstab.remove_entry(swap_entry)
unit-cassandra-0[17198]: 2015-02-17 18:55:26 INFO unit.cassandra/0.install logger.go:40 File "/var/lib/juju/agents/unit-cassandra-0/charm/hooks/charmhelpers/core/fstab.py", line 108, in remove_entry
unit-cassandra-0[17198]: 2015-02-17 18:55:26 INFO unit.cassandra/0.install logger.go:40 if self._hydrate_entry(line) == entry:
unit-cassandra-0[17198]: 2015-02-17 18:55:26 INFO unit.cassandra/0.install logger.go:40 File "/var/lib/juju/agents/unit-cassandra-0/charm/hooks/charmhelpers/core/fstab.py", line 72, in _hydrate_entry
unit-cassandra-0[17198]: 2015-02-17 18:55:26 INFO unit.cassandra/0.install logger.go:40 line.strip("\n").split()))
unit-cassandra-0[17198]: 2015-02-17 18:55:26 INFO unit.cassandra/0.install logger.go:40 TypeError: __init__() missing 4 required positional arguments: 'device', 'mountpoint', 'filesystem', and 'options'
