* Add spacy.errors module
* Update deprecation and user warnings
* Replace errors and asserts with new error message system
* Remove redundant asserts
* Fix whitespace
* Add messages for print/util.prints statements
* Fix typo
* Fix typos
* Move CLI messages to spacy.cli._messages
* Add decorator to display error code with message
An implementation like this is nice because it only modifies the string when it's retrieved from the containing class – so we don't have to worry about manipulating tracebacks etc.
* Remove unused link in spacy.about
* Update errors for invalid pipeline components
* Improve error for unknown factories
* Add displaCy warnings
* Update formatting consistency
* Move error message to spacy.errors
* Update errors and check if doc returned by component is None
Check for is_symlink() to also overwrite invalid and outdated symlinks. Also show better error message if link path exists but is not symlink (i.e. file or directory).
On fresh install via subprocess, pip.get_installed_distributions()
won't show new model, so is_package check in link command fails.
Solution for now is to get model package path explicitly and pass it to
link command.
Otherwise, formatting the success message with model_path.as_posix()
fails when using a local path for linking (linking still works, but the
error message is confusing)
