REF/CLN: pandas/io/pytables.py
- [ ] closes #xxxx
- [ ] tests added / passed
- [ ] passes `black pandas`
- [ ] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

Clean-up and minor refactor of ``pandas/io/pytables.py``.
- Extract method ``_identify_group``
- Clean-up some docstrings (spacing)
- Use suppress instead of try/except/pass
- Format error message using dedent
- Remove unnecessary empty lines as they compromise readability of some blocks
thanks @ivanovmg 