Use restructuredtext-lint instead of duplication

Now that the restructuredtext-lint project has fixed
its code we can remove our temporary copy of the logic
that library was providing to catch errors and warning that
are emitted when the rst structure is invalid.

Change-Id: I2fadde86ff0b2c8fbb6c828535da19e097f1894e

doc8/parser.py

@@ -19,6 +19,7 @@
 import errno
 import os
 
+import restructuredtext_lint as rl
 import six
 
 from docutils import core
@@ -53,49 +54,8 @@ class ParsedFile(object):
     def errors(self):
         if self._errors is not None:
             return self._errors
-        # Borrowed from pypi package restructuredtext-lint but modified to work
-        # better when there exists fatal/critical errors.
-        pub = core.Publisher(None, None, None, settings=None)
-        pub.set_components('standalone', 'restructuredtext', 'pseudoxml')
-        defaults = dict(self._defaults)
-        settings = pub.get_settings(**defaults)
-        pub.set_io()
-        reader = pub.reader
-        document = utils.new_document(self.filename, settings)
-        document.reporter.stream = None
-        # Collect errors via an observer
-        errors = []
-        def error_collector(data):
-            # Mutate the data since it was just generated
-            data.line = data['line']
-            data.source = data['source']
-            data.level = data['level']
-            data.type = data['type']
-            data.message = docutils_nodes.Element.astext(data.children[0])
-            data.full_message = docutils_nodes.Element.astext(data)
-            # Save the error
-            errors.append(data)
-        document.reporter.attach_observer(error_collector)
-        reader.parser.parse(self.contents, document)
-        document.transformer.populate_from_components(
-            (pub.source, pub.reader, pub.reader.parser, pub.writer,
-             pub.destination))
-        transformer = document.transformer
-        while transformer.transforms:
-            if not transformer.sorted:
-                # Unsorted initially, and whenever a transform is added.
-                transformer.transforms.sort()
-                transformer.transforms.reverse()
-                transformer.sorted = True
-            transform = transformer.transforms.pop()
-            priority, transform_class, pending, kwargs = transform
-            transform = transform_class(transformer.document,
-                                        startnode=pending)
-            transform.apply(**kwargs)
-            transformer.applied.append((priority, transform_class,
-                                        pending, kwargs))
-        self._errors = errors
-        return errors
+        self._errors = rl.lint(self.contents, filepath=self.filename)
+        return self._errors
 
     @property
     def document(self):

setup.py

@@ -41,6 +41,7 @@ setup(
     install_requires=[
         'argparse',
         'docutils',
+        'restructuredtext-lint>=0.7',
         'six',
         'stevedore',
     ],