Drop support for Home and XDG config files

This has been a huge support burden for us. I seriously considered doing
this in 3.0 but caved to a vocal minority and the desire to keep as much
backwards compatibility as possible. At this point, however, I'm done
witnessing the abuse Anthony has to suffer over this and I'm done with
the undue hostility that people who don't bother to read the docs
display. Hopefully, this eases that a bit.

docs/source/internal/option_handling.rst

@@ -129,13 +129,8 @@ In |Flake8| 2, configuration file discovery and management was handled by
 pep8.  In pep8's 1.6 release series, it drastically broke how discovery and
 merging worked (as a result of trying to improve it). To avoid a dependency
 breaking |Flake8| again in the future, we have created our own discovery and
-management.
-As part of managing this ourselves, we decided to change management/discovery
-for 3.0.0. We have done the following:
-
-- User files (files stored in a user's home directory or in the XDG directory
-  inside their home directory) are the first files read. For example, if the
-  user has a ``~/.flake8`` file, we will read that first.
+management in 3.0.0. In 4.0.0 we have once again changed how this works and we
+removed support for user-level config files.
 
 - Project files (files stored in the current directory) are read next and
   merged on top of the user file. In other words, configuration in project
@@ -157,7 +152,7 @@ To facilitate the configuration file management, we've taken a different
 approach to discovery and management of files than pep8. In pep8 1.5, 1.6, and
 1.7 configuration discovery and management was centralized in `66 lines of
 very terse python`_ which was confusing and not very explicit. The terseness
-of this function (|Flake8|'s authors believe) caused the confusion and
+of this function (|Flake8| 3.0.0's authors believe) caused the confusion and
 problems with pep8's 1.6 series. As such, |Flake8| has separated out
 discovery, management, and merging into a module to make reasoning about each
 of these pieces easier and more explicit (as well as easier to test).
@@ -176,23 +171,19 @@ to parse those configuration files.
 .. note:: ``local_config_files`` also filters out non-existent files.
 
 Configuration file merging and managemnt is controlled by the
-:class:`~flake8.options.config.MergedConfigParser`. This requires the instance
+:class:`~flake8.options.config.ConfigParser`. This requires the instance
 of :class:`~flake8.options.manager.OptionManager` that the program is using,
 the list of appended config files, and the list of extra arguments. This
 object is currently the sole user of the
 :class:`~flake8.options.config.ConfigFileFinder` object. It appropriately
 initializes the object and uses it in each of
 
-- :meth:`~flake8.options.config.MergedConfigParser.parse_cli_config`
-- :meth:`~flake8.options.config.MergedConfigParser.parse_local_config`
-- :meth:`~flake8.options.config.MergedConfigParser.parse_user_config`
+- :meth:`~flake8.options.config.ConfigParser.parse_cli_config`
+- :meth:`~flake8.options.config.ConfigParser.parse_local_config`
 
-Finally,
-:meth:`~flake8.options.config.MergedConfigParser.merge_user_and_local_config`
-takes the user and local configuration files that are parsed by
-:meth:`~flake8.options.config.MergedConfigParser.parse_local_config` and
-:meth:`~flake8.options.config.MergedConfigParser.parse_user_config`. The
-main usage of the ``MergedConfigParser`` is in
+Finally, :meth:`~flake8.options.config.ConfigParser.parse` returns the
+appropriate configuration dictionary for this execution of |Flake8|. The
+main usage of the ``ConfigParser`` is in
 :func:`~flake8.options.aggregator.aggregate_options`.
 
 Aggregating Configuration File and Command Line Arguments
@@ -201,7 +192,7 @@ Aggregating Configuration File and Command Line Arguments
 :func:`~flake8.options.aggregator.aggregate_options` accepts an instance of
 :class:`~flake8.options.manager.OptionManager` and does the work to parse the
 command-line arguments passed by the user necessary for creating an instance
-of :class:`~flake8.options.config.MergedConfigParser`.
+of :class:`~flake8.options.config.ConfigParser`.
 
 After parsing the configuration file, we determine the default ignore list. We
 use the defaults from the OptionManager and update those with the parsed
@@ -229,6 +220,6 @@ API Documentation
     :members:
     :special-members:
 
-.. autoclass:: flake8.options.config.MergedConfigParser
+.. autoclass:: flake8.options.config.ConfigParser
     :members:
     :special-members:

docs/source/release-notes/4.0.0.rst

@@ -0,0 +1,16 @@
+4.0.0 -- 202x-mm-dd
+-------------------
+
+You can view the `4.0.0 milestone`_ on GitHub for more details.
+
+Backwards Incompatible Changes
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+- Due to constant confusion by users, user-level |Flake8| configuration files
+  are no longer supported. Files will not be searched for in the user's home
+  directory (e.g., ``~/.flake8``) nor in the XDG config directory (e.g.,
+  ``~/.config/flake8``).
+
+.. all links
+.. _4.0.0 milestone:
+    https://github.com/PyCQA/flake8/milestone/39

docs/source/release-notes/index.rst

@@ -5,6 +5,12 @@
 All of the release notes that have been recorded for Flake8 are organized here
 with the newest releases first.
 
+4.x Release Series
+==================
+
+.. toctree::
+   4.0.0
+
 3.x Release Series
 ==================