More information on numexpr failure

[kreczko]

Currently, if something goes wrong while evaluating a numexpr expression, the error message is not very helpful:

  File "/mnt/c/Workspace/fast-carpenter/fast_carpenter/expressions.py", line 115, in evaluate
    result = numexpr.evaluate(cleaned_expression, local_dict=adaptor)
  File "/software/miniconda/envs/hep_py/lib/python3.7/site-packages/numexpr/necompiler.py", line 822, in evaluate
    zip(names, arguments)]
  File "/software/miniconda/envs/hep_py/lib/python3.7/site-packages/numexpr/necompiler.py", line 821, in <listcomp>
    signature = [(name, getType(arg)) for (name, arg) in
  File "/software/miniconda/envs/hep_py/lib/python3.7/site-packages/numexpr/necompiler.py", line 703, in getType
    raise ValueError("unknown type %s" % a.dtype.name)
ValueError: unknown type object

Instead, it would be useful to catch the exception in

result = numexpr.evaluate(cleaned_expression, local_dict=adaptor)

prepend the cleaned_expression to the exception message and re-raise the exception.

E.g.

Error in <stage>.variables."<name>": Unable to evaluate "<expression>".
<numexpr error message>