clean up data.py

[cpcloud]

• remove isinstance(x, str) checks
• handle urls with context managers
• get rid of Exception and use appropriate exception types
• pep8
• remove redundant parens in conditionals
• remove \ style line joins
• range -> xrange
• functions should not exit after a warning with None they should raise an exception
• turn all the str + style concats into format strings
• remove redundant calls to str
• remove exception handlers with no exception type
• replace calls to __setattr__ and __getattribute__ with setattr and getattr
• code coverage at 99%

This should remove the connection reset by peer testing error and I thought I would perform a little housekeeping while I was at it.

[jreback]

I see that you moved #4002 to 0.12, this too?

[cpcloud]

yep thanks

[cpcloud]

this is getting a heaping helping of DRY