[yt-dev] Issue #948: FITSProjection fails with ValueError: 'code_length' did not parse as fits unit (yt_analysis/yt)

[Kacper Kowalik]

New issue 948: FITSProjection fails with ValueError: 'code_length' did not parse as fits unit
https://bitbucket.org/yt_analysis/yt/issue/948/fitsprojection-fails-with-valueerror

Kacper Kowalik:

Following script:

```
#!python

import yt
from yt.utilities.fits_image import FITSProjection

ds = yt.load("MHDSloshing/virgo_low_res.0054.vtk",
             parameters={"length_unit": (1.0, "Mpc"),
                         "mass_unit": (1.0e14, "Msun"),
                         "time_unit": (1.0, "Myr")})
prj_fits = FITSProjection(ds, "z", ["temperature"], weight_field="density")
```

yields

```
#!text

Traceback (most recent call last):
  File "foo.py", line 8, in <module>
    prj_fits = FITSProjection(ds, "z", ["temperature"], weight_field="density")
  File "yt/utilities/fits_image.py", line 474, in __init__
    image_res=image_res)
  File "yt/utilities/fits_image.py", line 358, in construct_image
    w.wcs.cunit = cunit
  File "/usr/lib64/python2.7/site-packages/astropy/units/core.py", line 1735, in __call__
    raise ValueError(msg)
ValueError: 'code_length' did not parse as fits unit: At col 0, Unit u'code_length' not supported by the FITS standard. 
```

I'm using *astropy-0.4* and *yt* rev: 09a0a10893ef

Responsible: jzuhone