Download.rvcurve creates file if object not found

[cgelino]

If you try to download an RV curve for an object that doesn't have an RV curve, Download.rvcurve will save a file with the input object name and the status returned by the call will be "ok'. Example:

from hiresprv.download import Download
data = Download('prv.cookies', './')
rtn = data.rvcurve('garbage')
print(rtn)

{'status': 'ok', 'msg': ''}

A file named vstgarbage.csv is created on disk. This file contains {"status":"Failed to open requested file vstgarbage.csv in your workspace."}. It would be much more useful to have Download.rvcurve return {'status':'Failed', 'msg':'Failed to open requested file vstgarbage.csv in your workspace.'} in this case and for no file to be written out. The documentation for rvcurve says that objname must match an entry in TARGET column, but clearly it will happily process any name you give it.