RuntimeError exposed to user

[mjordan]

When running bag-split.py in unsplit mode, a RuntimeError is raised and exposed to the user:

python bag-split.py unsplit /home/mark/Downloads/bagsplittest/marksbag_split/
Validating bag marksbag_2... success.
Validating bag marksbag_1... success.
Validating bag marksbag_0... success.
Copying payload from marksbag_0...
Copying payload from marksbag_1...
Copying payload from marksbag_2...
New manifest does NOT appear consistent with the split manifests!
Traceback (most recent call last):
File "bag-split.py", line 344, in <module>
unsplit(bag_path, args.output_dir, args.no_verify)
File "bag-split.py", line 237, in unsplit
raise RuntimeError("merged bag manifest inconsistent with split " \
RuntimeError: merged bag manifest inconsistent with split manifests 

It might be worth using a try/except around lines 321-238 or some other way of printing a more friendly form of the message to the user (similar to the "New manifest does NOT appear consistent with the split manifests!" message).