Ensembl-prodinf-core

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- Better error display from failed handover client submission
- Better handling HTTRequestError
- Prevent HiveInstance from using nested sessions
- Update SQL Alchemy version and SQL Alchemy-utils

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- Fixed issues with hidden chars in perl strings

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- Fixed typo in `hive.py` module causing error in DC jobs status retrieval.

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- Requests version range instead of "Compatible" (>=2.4,<3)
- PyYAML version changed to comply with ensembl-py (PyYAML~=6.0)

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- Change `db_introspects` module
- `get_database_set()` and `get_table_set()` filters "match" instead of "search"

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- Fix tests and run them with pytest
- Update some functions and methods
- Automate test & deploy with Travis
- Fix setup.py to be PyPI compliant