Heasarc: trying votable

[volodymyrss]

in response to #2333 and #2349, this is an attempt to use VOTable backend of heasarc to resolve problems with unit conversion.
It needs to be determined if this is a viable approach.

[bsipocz]

you'll need to get rid of the Table_read workaround, too.

[volodymyrss]

Ok, yes.
Though I think it will be still needed for the fallback, old interface has no VOTable.

I copied the code from #2333 to a test:

https://github.com/oda-hub/astroquery/blob/b09c8b588bafa0078c2a6996b251af669a1a894d/astroquery/heasarc/tests/test_heasarc_remote.py#L108-L123

Currently it fails while trying to _convert_record2fits. Maybe if it starts with fits it's more compatible. Some investigation is needed.

[nkphysics]

you'll need to get rid of the Table_read workaround, too.

I have been trying to work on this conversion to VOTable on my own. Is there any other reason why we need to keep the Table_read function in other than silence the unit parsing?

For refernce:

def Table_read(*args, **kwargs):
    if commons.ASTROPY_LT_5_1:
        return Table.read(*args, **kwargs)
    else:
        return Table.read(*args, **kwargs, unit_parse_strict='silent')

I only ask since I in some testing with some of my own changes I've cut out this function and most tables work with VOTable perfectly fine without warnings.

I can submit a separate PR with more info if that would be more appropriate.

[pep8speaks]

Hello @volodymyrss! Thanks for updating this PR. We checked the lines you've touched for PEP 8 issues, and found:

• In the file astroquery/heasarc/tests/test_heasarc_remote.py:

Line 110:9: E265 block comment should start with '# '
Line 113:36: E225 missing whitespace around operator
Line 114:35: W291 trailing whitespace
Line 117:9: E265 block comment should start with '# '
Line 117:9: E303 too many blank lines (2)
Line 119:27: E261 at least two spaces before inline comment
Line 120:96: E251 unexpected spaces around keyword / parameter equals
Line 120:98: E251 unexpected spaces around keyword / parameter equals
Line 120:111: E251 unexpected spaces around keyword / parameter equals
Line 120:113: E251 unexpected spaces around keyword / parameter equals
Line 122:9: E265 block comment should start with '# '
Line 122:60: W291 trailing whitespace
Line 123:58: E251 unexpected spaces around keyword / parameter equals
Line 123:60: E251 unexpected spaces around keyword / parameter equals