raise KeyError on missing keywords in model names #161

[arrrobase]

Solves #161

[svdavid]

Basically fine. Though the language is funny. Shouldn't the log report "Error" rather than "skipping"? Also typically we've been using code like raise ValueError("keyword not found")

[arrrobase]

I'll amend the commit to fix the log message.

My understanding was that a simple raise will raise the actual error that occurred in the try block, whereas a new raise KeyError('message') will generate a new error that gets added to the exception chain. If the error context is complicated enough the new error can make it hard to see what's happening.

https://docs.python.org/3/reference/simple_stmts.html#raise https://docs.python.org/3/tutorial/errors.html#raising-exceptions

I can replace it with raise ValueError("keyword not found") if that's preferable.

[arrrobase]

Added custom error KeywordMissingError. Raised if keyword is not in registry. The stack trace now looks like this for the modelname fakehead.ozgf.fs100.ch18-ld-sev_dlog-wc.18x3.g-fir.3x15-lvl.1-dexp.1_init-basic:

[nems.xform_helper INFO] Initializing modelspec(s) for recording/model None/fakehead.ozgf.fs100.ch18-ld-sev_dlog-wc.18x3.g-fir.3x15-lvl.1-dexp.1_init-basic...
Traceback (most recent call last):
  File "/home/tomlinsa/anaconda3/envs/nems/lib/python3.6/site-packages/IPython/core/interactiveshell.py", line 3326, in run_code
    exec(code_obj, self.user_global_ns, self.user_ns)
  File "<ipython-input-2-4d4fc6e72af3>", line 1, in <module>
    runfile('/home/tomlinsa/.PyCharmCE2019.3/config/scratches/scratch.py', wdir='/home/tomlinsa/.PyCharmCE2019.3/config/scratches')
  File "/snap/pycharm-community/169/plugins/python-ce/helpers/pydev/_pydev_bundle/pydev_umd.py", line 197, in runfile
    pydev_imports.execfile(filename, global_vars, local_vars)  # execute the script
  File "/snap/pycharm-community/169/plugins/python-ce/helpers/pydev/_pydev_imps/_pydev_execfile.py", line 18, in execfile
    exec(compile(contents+"\n", file, 'exec'), glob, loc)
  File "/home/tomlinsa/.PyCharmCE2019.3/config/scratches/scratch.py", line 7, in <module>
    xfspec, ctx = fit_model_xform(cellid, batch, modelname, save_file=False, saveInDB=False)
  File "/home/tomlinsa/code/NEMS/nems/xform_helper.py", line 178, in fit_model_xform
    autoPlot=autoPlot)
  File "/home/tomlinsa/code/NEMS/nems/xform_helper.py", line 97, in generate_xforms_spec
    xfspec.extend(_parse_kw_string(load_keywords, xforms_lib))
  File "/home/tomlinsa/code/NEMS/nems/xform_helper.py", line 279, in _parse_kw_string
    xfspec.extend(registry[kw])
  File "/home/tomlinsa/code/NEMS/nems/registry.py", line 69, in __getitem__
    kw = self.lookup(kw_string)
  File "/home/tomlinsa/code/NEMS/nems/registry.py", line 98, in lookup
    raise KeywordMissingError(kw_head)
nems.registry.KeywordMissingError: "fakehead" could not be found in the keyword registry.