Merge pull request pytest-dev#909 from flub/assertdoc

Update docs to represent reality

Author: nicoddemus

doc/en/assert.txt

@@ -228,9 +228,7 @@ Reporting details about a failing assertion is achieved either by rewriting
 assert statements before they are run or re-evaluating the assert expression and
 recording the intermediate values. Which technique is used depends on the
 location of the assert, ``pytest`` configuration, and Python version being used
-to run ``pytest``.  Note that for assert statements with a manually provided
-message, i.e. ``assert expr, message``, no assertion introspection takes place
-and the manually provided message will be rendered in tracebacks.
+to run ``pytest``.
 
 By default, if the Python version is greater than or equal to 2.6, ``pytest``
 rewrites assert statements in test modules. Rewritten assert statements put