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+Upgrading Pyramid
+=================
+
+When a new version of Pyramid is released, it will sometimes deprecate an old
+feature or remove an already-deprecated feature.  When features are removed
+from Pyramid, applications that depend on those features will begin to break.
+This chapter explains how to ensure your Pyramid applications keep working
+when you upgrade the Pyramid version you're using.
+
+.. sidebar::   About Release Numbering
+
+   Conventionally, application version numbering in Python is described as
+   ``major.minor.micro``.  If your Pyramid version is "1.2.3", it means
+   you're running a version of Pyramid with the major version "1", the minor
+   version "2" and the micro version "3".  A "major" release is one that
+   increments the first-dot number; 2.X.X might follow 1.X.X.  A "minor"
+   release is one that increments the second-dot number; 1.3.X might follow
+   1.2.X.  A "micro" release is one that increments the third-dot number;
+   1.2.3 might follow 1.2.2.  In general, micro releases are "bugfix-only",
+   and contain no new features, minor releases contain new features but are
+   largely backwards compatible with older versions, and a major release
+   indicates a large set of backwards incompatibilities.
+
+The Pyramid core team is conservative when it comes to removing features.  We
+don't remove features unnecessarily, but we're human, and we make mistakes
+which cause some features to be evolutionary dead ends.  Though we are
+willing to support dead-end features for some amount of time, some eventually
+have to be removed when the cost of supporting them outweighs the benefit of
+keeping them around, because each feature in Pyramid represents a certain
+documentation and maintenance burden.
+
+Deprecation and Removal Policy
+------------------------------
+
+When a feature is scheduled for removal from Pyramid or any of its official
+add-ons, the core development team takes these steps:
+
+- Using the feature will begin to generate a `DeprecationWarning`, indicating
+  the version in which the feature became deprecated.
+
+- A note is added to the documentation indicating that the feature is
+  deprecated.
+
+- A note is added to the :ref:`changelog` about the deprecation.
+
+When a deprecated feature is eventually removed:
+
+- The feature is removed.
+
+- A note is added to the :ref:`changelog` about the removal.
+
+Features are never removed in *micro* releases.  They are only removed in
+minor and major releases.  Deprecated features are kept around for at least
+*three* minor releases from the time the feature became deprecated.
+Therefore, if a feature is added in Pyramid 1.0, but it's deprecated in
+Pyramid 1.1, it will be kept around through all 1.1.X releases, all 1.2.X
+releases and all 1.3.X releases.  It will finally be removed in the first
+1.4.X release.
+
+Sometimes features are "docs-deprecated" instead of formally deprecated.
+This means that the feature will be kept around indefinitely, but it will be
+removed from the documentation or a note will be added to the documentation
+telling folks to use some other newer feature.  This happens when the cost of
+keeping an old feature around is very minimal and the support and
+documentation burden is very low.  For example, we might rename a function
+that is an API without changing the arguments it accepts.  In this case,
+we'll often rename the function, and change the docs to point at the new
+function name, but leave around a backwards compatibility alias to the old
+function name so older code doesn't break.
+
+"Docs deprecated" features tend to work "forever", meaning that they won't be
+removed, and they'll never generate a deprecation warning.  However, such
+changes are noted in the :ref:`changelog`, so it's possible to know that you
+should change older spellings to newer ones to ensure that people reading
+your code can find the APIs you're using in the Pyramid docs.
+
+Consulting the Change History
+-----------------------------
+
+Your first line of defense against application failures caused by upgrading
+to a newer Pyramid release is always to read the :ref:`changelog`.  to find
+the deprecations and removals for each release between the release you're
+currently running and the one you wish to upgrade to.  The change history
+notes every deprecation within a ``Deprecation`` section and every removal
+within a ``Backwards Incompatibilies`` section for each release.
+
+The change history often contains instructions for changing your code to
+avoid deprecation warnings and how to change docs-deprecated spellings to
+newer ones.  You can follow along with each deprecation explanation in the
+change history, simply doing a grep or other code search to your application,
+using the change log examples to remediate each potential problem.
+
+.. _testing_under_new_release:
+
+Testing Your Application Under a New Pyramid Release
+----------------------------------------------------
+
+Once you've upgraded your application to a new Pyramid release and you've
+remediated as much as possible by using the change history notes, you'll want
+to run your application's tests (see :ref:`running_tests`) in such a way that
+you can see DeprecationWarnings printed to the console when the tests run.
+
+.. code-block:: bash
+
+   $ python -Wd setup.py test -q
+
+The ``-Wd`` argument is an argument that tells Python to print deprecation
+warnings to the console.  Note that the ``-Wd`` flag is only required for
+Python 2.7 and better: Python versions 2.6 and older print deprecation
+warnings to the console by default.  See `the Python -W flag documentation
+<http://docs.python.org/using/cmdline.html#cmdoption-W>`_ for more
+information.
+
+As your tests run, deprecation warnings will be printed to the console
+explaining the deprecation and providing instructions about how to prevent
+the deprecation warning from being issued.  For example:
+
+.. code-block:: text
+
+   $ python -Wd setup.py test -q
+   # .. elided ...
+   running build_ext
+   /home/chrism/projects/pyramid/env27/myproj/myproj/views.py:3: DeprecationWarning: static: The "pyramid.view.static" class is deprecated as of Pyramid 1.1; use the "pyramid.static.static_view" class instead with the "use_subpath" argument set to True.
+     from pyramid.view import static
+   .
+   ----------------------------------------------------------------------
+   Ran 1 test in 0.014s
+   
+   OK
+
+In the above case, it's line #3 in the ``myproj.views`` module (``from
+pyramid.view import static``) that is causing the problem:
+
+.. code-block:: python
+   :linenos:
+
+    from pyramid.view import view_config
+
+    from pyramid.view import static
+    myview = static('static', 'static')
+
+The deprecation warning tells me how to fix it, so I can change the code to
+do things the newer way:
+
+.. code-block:: python
+   :linenos:
+
+    from pyramid.view. import view_config
+
+    from pyramid.static import static_view
+    myview = static_view('static', 'static', use_subpath=True)
+
+When I run the tests again, the deprecation warning is no longer printed to
+my console:
+
+.. code-block:: text
+
+   $ python -Wd setup.py test -q
+   # .. elided ...
+   running build_ext
+   .
+   ----------------------------------------------------------------------
+   Ran 1 test in 0.014s
+   
+   OK
+
+
+My Application Doesn't Have Any Tests or Has Few Tests
+------------------------------------------------------
+
+If your application has no tests, or has only moderate test coverage, running
+tests won't tell you very much, because the Pyramid codepaths that generate
+deprecation warnings won't be executed.
+
+In this circumstance, you can start your application interactively under a
+server run with the ``PYTHONWARNINGS`` environment variable set to
+``default``.  On UNIX, you can do that via:
+
+.. code-block:: bash
+
+   $ PYTHONWARNINGS=default bin/pserve development.ini
+
+On Windows, you need to issue two commands:
+
+.. code-block:: bash
+
+   C:\> set PYTHONWARNINGS=default
+   C:\> Scripts/pserve.exe development.ini
+
+At this point, it's ensured that deprecation warnings will be printed to the
+console whenever a codepath is hit that generates one.  You can then click
+around in your application interactively to try to generate them, and
+remediate as explained in :ref:`testing_under_new_release`.
+
+See `the PYTHONWARNINGS environment variable documentation
+<http://docs.python.org/using/cmdline.html#envvar-PYTHONWARNINGS>`_ or `the
+Python -W flag documentation
+<http://docs.python.org/using/cmdline.html#cmdoption-W>`_ for more
+information.
+
+Upgrading to the Very Latest Pyramid Release
+--------------------------------------------
+
+When you upgrade your application to the very most recent Pyramid release,
+it's advisable to upgrade step-wise through each most recent minor release,
+beginning with the one that you know your application currently runs under,
+and ending on the most recent release.  For example, if your application is
+running in production on Pyramid 1.2.1, and the most recent Pyramid 1.3
+release is Pyramid 1.3.3, and the most recent Pyramid release is 1.4.4, it's
+advisable to do this:
+
+- Upgrade your environment to the most recent 1.2 release.  For example, the
+  most recent 1.2 release might be 1.2.3, so upgrade to it.  Then run your
+  application's tests under 1.2.3 as described in
+  :ref:`testing_under_new_release`.  Note any deprecation warnings and
+  remediate.
+
+- Upgrade to the most recent 1.3 release, 1.3.3.  Run your application's
+  tests, note any deprecation warnings and remediate.
+
+- Upgrade to 1.4.4.  Run your application's tests, note any deprecation
+  warnings and remediate.
+
+If you skip testing your application under each minor release (for example if
+you upgrade directly from 1.2.1 to 1.4.4), you might miss a deprecation
+warning and waste more time trying to figure out an error caused by a feature
+removal than it would take to upgrade stepwise through each minor release.
+
+