[yt-dev] Issue #855: [flash] undefined 'unitsystems' (yt_analysis/yt)

[Kacper Kowalik]

New issue 855: [flash] undefined 'unitsystems'
https://bitbucket.org/yt_analysis/yt/issue/855/flash-undefined-unitsystems

Kacper Kowalik:

Pull request #1003 causes:

```
#!python
import yt
yt.load("Orbit/orbit_hdf5_chk_0000")
```

to fail with:

```
#!text
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "yt/src/yt-my/yt/convenience.py", line 80, in load
    return output_type_registry[candidates[0]](*args, **kwargs)
  File "yt/src/yt-my/yt/frontends/flash/data_structures.py", line 206, in __init__
    Dataset.__init__(self, filename, dataset_type)
  File "yt/src/yt-my/yt/data_objects/static_output.py", line 186, in __init__
    self.set_units()
  File "yt/src/yt-my/yt/data_objects/static_output.py", line 603, in set_units
    self.set_code_units()
  File "yt/src/yt-my/yt/frontends/flash/data_structures.py", line 241, in set_code_units
    super(FLASHDataset, self).set_code_units()
  File "yt/src/yt-my/yt/data_objects/static_output.py", line 631, in set_code_units
    self._set_code_unit_attributes()
  File "yt/src/yt-my/yt/frontends/flash/data_structures.py", line 214, in _set_code_unit_attributes
    if self.parameters['unitsystem'].lower() == "cgs":
KeyError: 'unitsystem'
```

Responsible: jzuhone