@falkamelung noted a race condition in #106 due to non-atomic directory
checking followed by os.makedirs. This pattern exists in many places
in the codebase so I went ahead and replaced the rest of them.
The new exist_ok usage should be terser and more idiomatic.
ISCE_HOME was only used to get the location of the default logging config.
Lots of scripts were using boilerplate to set up this config, so I added
an `isce.logging` helper module which is the same as builtin python logging
but already has the configuration defaults set up for isce.
ISCE_HOME setup is retained in the toplevel `__init__.py`
but can now be removed without affecting functionality.
sssangha
Ryan Burns
Ryan Burns
Eric Gurrola