bpo-39429: Add a new "Python Development Mode" doc page (GH-18132)

1 files changed, 14 insertions, 2 deletions

diff --git a/Doc/library/exceptions.rst b/Doc/library/exceptions.rst
index 52a505e..df2cda9 100644
--- a/Doc/library/exceptions.rst
+++ b/Doc/library/exceptions.rst
@@ -688,6 +688,10 @@ The following exceptions are used as warning categories; see the
    Base class for warnings about deprecated features when those warnings are
    intended for other Python developers.
 
+   Ignored by the default warning filters, except in the ``__main__`` module
+   (:pep:`565`). Enabling the :ref:`Python Development Mode <devmode>` shows
+   this warning.
+
 
 .. exception:: PendingDeprecationWarning
 
@@ -699,6 +703,9 @@ The following exceptions are used as warning categories; see the
    upcoming deprecation is unusual, and :exc:`DeprecationWarning`
    is preferred for already active deprecations.
 
+   Ignored by the default warning filters. Enabling the :ref:`Python
+   Development Mode <devmode>` shows this warning.
+
 
 .. exception:: SyntaxWarning
 
@@ -720,6 +727,9 @@ The following exceptions are used as warning categories; see the
 
    Base class for warnings about probable mistakes in module imports.
 
+   Ignored by the default warning filters. Enabling the :ref:`Python
+   Development Mode <devmode>` shows this warning.
+
 
 .. exception:: UnicodeWarning
 
@@ -733,8 +743,10 @@ The following exceptions are used as warning categories; see the
 
 .. exception:: ResourceWarning
 
-   Base class for warnings related to resource usage. Ignored by the default
-   warning filters.
+   Base class for warnings related to resource usage.
+
+   Ignored by the default warning filters. Enabling the :ref:`Python
+   Development Mode <devmode>` shows this warning.
 
    .. versionadded:: 3.2