Miscellaneous changes

[T-Nicholls]

This is pretty much everything that was left on my todo list for pytac.

If you remember we discovered that our errors were being chained rather than replaced, when using Python 3, e.g.

>>> lattice.get_value('not_a_field')
Traceback (most recent call last):
  File "/home/jzs47954/git/pytac/pytac/data_source.py", line 315, in get_value
    throw (bool): if True, ControlSystemException will be raised on
KeyError: 'not_a_field'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/jzs47954/git/pytac/pytac/data_source.py", line 196, in get_value
    if units == pytac.DEFAULT:
  File "/home/jzs47954/git/pytac/pytac/data_source.py", line 318, in get_value
    Returns:
pytac.exceptions.FieldException: No field not_a_field on data source <pytac.data_source.DeviceDataSource object at 0x7fb0ba8a9cc0>.

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/jzs47954/git/pytac/pytac/lattice.py", line 174, in get_value
    try:
  File "/home/jzs47954/git/pytac/pytac/data_source.py", line 204, in get_value
    target=units)
pytac.exceptions.FieldException: No field not_a_field on manager <pytac.data_source.DataSourceManager object at 0x7fb0ba88c080>.

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/jzs47954/git/pytac/pytac/lattice.py", line 180, in get_value
    except FieldException:
pytac.exceptions.FieldException: Lattice <pytac.lattice.EpicsLattice object at 0x7fb0ba88c128> does not have field not_a_field on data source default

According to pep3134 this is the intended behaviour now; pep415 gives ways to avoid this, but they are not compatible with python 2.7 as far as I can tell. So for it seems like we are stuck with this behaviour.

[coveralls]

Coverage increased (+0.0007%) to 99.846% when pulling ae630a6 on T-Nicholls:miscChanges into 48a2522 on dls-controls:master.

[willrogers]

Generally looks good, I've made a few comments that you can respond to.

[willrogers]

How about:

To see a coverage report and style violations, you can use pytest-cov, pep8 and pyflakes:

[T-Nicholls]

I thought that we use flake8 instead of pep8 and pyflakes.
So perhaps:

To see a coverage report, check pytest-cov:
 $ python -m pytest --cov-report term-missing --cov=pytac

To see style violations, use flake8:
 $ flake8

Or we could use this plugin:

To see a coverage report and style violations, you can use pytest-cov and flake8:
 $ python -m pytest --cov-report term-missing --cov=pytac --flake8