TST: add tests for Series/Panel with non-unique index in to_hdf with fixed format

[jreback]

xref #7788

[jreback]

cc @filmor

[filmor]

I'll look into this.

[filmor]

Would you mind having a look at the build failures? https://travis-ci.org/filmor/pandas/builds/32934493

The only changes I did against master are these: filmor@1dcd687

I don't know why test_wide_table_dups is failing now and it also seems like the table format can't handle non-unique indexes for panels as well. Is this by design?

[jreback]

iirc this is not possible to store these non unique indexers - well u can store them but the non uniques are filtered out in the way back (they are stored in a flattened way(

trace the reading and u will see -

[filmor]

Okay, but in this case it should (like I outlined in #7788) raise an exception for all of these cases. What is the intended behaviour?

Also, this doesn't explain why test_wide_table_dups fails.

[jreback]

you need to trace it. I don't really remember exactly what it does in the case of non-unique axes for table format.

[jreback]

@filmor ?