Pip-licenses

* Suppress errors when opening license files

* Implement new option `--format=plain-vertical`
* Support for outputting license file named `COPYING *`

* Better license file open handling in Python 3

* Dropped support Python 2.7
* Breaking changes
* Removed migration path to obsolete options
* `--from-classifier`
* `--format-markdown`
* `--format-rst`
* `--format-confluence`
* `--format-html`
* `--format-json`
* Implement new option `--no-license-path`

* Supports compatibility to work with either PTable or prettytable

* Implement new option `--output-file`
* Clarified support for Python 3.8