Document fixes for lint errors

howto/code/lint/index.rst
howto/code/lint/fix-errors
--------------------------
  o Added a new 'fixing-errors' section in 'howto: lint'.

howto/code/lint/fix-errors/sphinx/spelling
howto/code/lint/fix-errors/yamllint
------------------------------------------
  o Document a few known fixes for common problems.

requirements.txt
----------------
  o Capture detail for a python upgrade error uncovered by 'make reload'.
  o libdoc command for robot/robotframework having issues.

Change-Id: Iaa700327d374b6040841cbfc98f76ba95c16c799
Signed-off-by: Joey Armstrong <jarmstrong@linuxfoundation.org>
diff --git a/howto/code/lint/fix-errors/yamllint/long-lines.rst b/howto/code/lint/fix-errors/yamllint/long-lines.rst
new file mode 100644
index 0000000..e4d16bf
--- /dev/null
+++ b/howto/code/lint/fix-errors/yamllint/long-lines.rst
@@ -0,0 +1,15 @@
+LINT: Spelling exclusions
+=========================
+
+.. code:: bash
+
+   % make lint-yaml
+
+Folding
+-------
+
+- >, >-, >+
+
+.. seealso::
+
+- https://yaml-multiline.info/