filename read error in pdfdataset.py

[stevenhua0320]

When running script,. there is indexing error in reading the filename.
File "/Users/huarundong/dbs/diffpy.srmise/diffpy.srmise/src/diffpy/srmise/pdfdataset.py", line 407, in <module>
filename = sys.argv[1]
~~~~~~~~^^^
IndexError: list index out of range

[Ainamacar]

This particular test script was intended to run with a command-line argument, a path to a file with a readable PDF. If you just run pdfdataset.py alone then sys.argv[1] does not exist. I'm sure you have access to many of these, but the repository already includes several in doc/examples/data. All the script does is read in the data then prints to the console the file's PDF metadata (e.g. qmax) and 4 columns of data.

As a temporary measure, include a path to such a file if you just want this script to run without error. However, this entire if __name__ == "__main__": block should be removed and replaced with a proper test. The code in this file is taken nearly verbatim from PDFgui (see file header) so you might be able to borrow tests from that project.