Created a basic system test checking the reading of a non-PDB file by structure.read_pdb.
........ r13984 | bugman | 2011-07-29 10:06:14 +0200 (Fri, 29 Jul 2011) | 5 lines
Fix for structure.read_pdb for when the file contains no PDB data.
This is now caught, and a warning is given and the function exists cleanly.
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