Prevent VOTable validator from crashing when system sends SIGKILL during xmllint.
__repr__ method in Table now also returns the units

updated doctests (for __repr__ table)

updated doctests (for __repr__ table), corrected

modifying table_repr_method

show units only when atleast one column is not None. + doctests updated.

show units only when atleast one column not None. + doctests updated.

removed quotes from 'None'.

some code standardization

added test for repr method, updated changes.rst

added doctest for repr method, updated chages.rst
Slight improvements to model string formatting

This deduplicates a lot of `__repr__` and `__str__` code for Model
and its subclasses, so there is more consistency between different
Model classes in what their `__repr__` and `__str__` output.
Also made some slight improvements to the previous output formats.
I still don't claim this to be perfect, but it's a step in a better
direction.  In particular I think displaying the different parameter
sets as a table is nice.

These changes are a prerequisite to another, potentially more
interesting change.
Fix #2398.  Support a mix of strings and quantities passed to the angle constructor.
change remote data tests to use astropy site instead of google
Merge pull request #2412 from eteq/fix-google-data-test

change remote data tests to use astropy site instead of google
Fixes one of the remote-data tests mentioned in #2290.  Adds a simple context manager for turn_internet_off/turn_internet_on so that this particular test can work regardless of whether --remote-data is in use.
Catch a possible timeout that could occur while reading response data on a slow connection.  Fixes one of the issues with --remote-data tests referenced in #2290 and #2332
Explicitly encode keys going into the URL cache db as UTF-8 just to be consistent
Fix a few examples of astropy.tests.helper.raises mistakenly being used like py.test raises (the latter works a context manager, the former previously did not).  But this also goes ahead an makes astropy.tests.helper.raises pass through to pytest.raises when used as a context manager.  A little ambiguous, but at the same time makes this mistake less likely.
For reasons that I don't care to investigate any further, the recwarn fixture wasn't working properly for this test, but catch_warnings seems to do the trick
Per https://github.com/astropy/astropy/issues/2290#issuecomment-40372069, removing this test as the required data file is no longer online.

Conflicts:

	astropy/vo/client/tests/test_vo.py
Merge pull request #2405 from embray/fix-disable-internet-test

Fixes several of the remote-data tests mentioned in #2290
Merge pull request #2379 from embray/model-repr

Slight improvements to model string formatting
Merge pull request #2180 from rastogitanuj/table_repr_method

__repr__ method in Table now also returns the units
Expanded VO catalog and database functionalities. Moved VO exceptions to a separate modules in client and validator. Changed inheritance to super. Updated doc and tests. Fixed codes for Python 3 compatibility and to complete coverage. Applied review comments.
Reduced default search radius for cone search validation to avoid large query results for xmllint.
Fixed failing tests because they do not always run in order.
Follow on to #2405 that handles some Python3-specific issues that slipped through the cracks
Merge pull request #2398 from mdboom/coordinates/mixed-strings

Different input formats for Angle confuse unit parsing