Add a release note to 3.0.0 about --exclude

When we rewrote Flake8 for 3.0, we unintentionally stopped forcibly
excluding some patterns regardless of what the user specified. This note
is added after the fact to make it easier for users to determine the
cause of any backwards incompatibility they might notice.

Closes #250

1 files changed, 14 insertions, 0 deletions

diff --git a/docs/source/release-notes/3.0.0.rst b/docs/source/release-notes/3.0.0.rst
index d335494..2cec53a 100644
--- a/docs/source/release-notes/3.0.0.rst
+++ b/docs/source/release-notes/3.0.0.rst
@@ -47,3 +47,17 @@
 - AST plugins can either be functions or classes and all plugins can now
   register options so long as there are callable attributes named as we
   expect.
+
+- Stop forcibly re-adding ``.tox``, ``.eggs``, and ``*.eggs`` to
+  ``--exclude``. Flake8 2.x started always appending those three patterns
+  to any exclude list (including the default and any user supplied list).
+  Flake8 3 has stopped adding these in, so you may see errors when upgrading
+  due to these patterns no longer being forcibly excluded by default if you
+  have your own exclude patterns specified.
+
+  To fix this, add the appropriate patterns to your exclude patterns list.
+
+  .. note::
+
+      This item was added in November of 2016, as a result of a bug
+      report.