Merge #7152: Clarify that ProxyHandler is added only if proxy settings are detected.

Behavior confirmation and initial patch by Jessica McKellar.

Doc/howto/urllib2.rst

@@ -504,9 +504,10 @@ than the URL you pass to .add_password() will also match. ::
 
     In the above example we only supplied our ``HTTPBasicAuthHandler`` to
     ``build_opener``. By default openers have the handlers for normal situations
-    -- ``ProxyHandler``, ``UnknownHandler``, ``HTTPHandler``,
+    -- ``ProxyHandler`` (if a proxy setting such as an :envvar:`http_proxy`
+    environment variable is set), ``UnknownHandler``, ``HTTPHandler``,
     ``HTTPDefaultErrorHandler``, ``HTTPRedirectHandler``, ``FTPHandler``,
-    ``FileHandler``, ``HTTPErrorProcessor``.
+    ``FileHandler``, ``DataHandler``, ``HTTPErrorProcessor``.
 
 ``top_level_url`` is in fact *either* a full URL (including the 'http:' scheme
 component and the hostname and optionally the port number)
@@ -521,7 +522,8 @@ Proxies
 =======
 
 **urllib** will auto-detect your proxy settings and use those. This is through
-the ``ProxyHandler`` which is part of the normal handler chain. Normally that's
+the ``ProxyHandler``, which is part of the normal handler chain when a proxy
+setting is detected.  Normally that's
 a good thing, but there are occasions when it may not be helpful [#]_. One way
 to do this is to setup our own ``ProxyHandler``, with no proxies defined. This
 is done using similar steps to setting up a `Basic Authentication`_ handler : ::

Doc/library/urllib.request.rst

@@ -87,8 +87,10 @@ The :mod:`urllib.request` module defines the following functions:
    the default installed global :class:`OpenerDirector` uses
    :class:`UnknownHandler` to ensure this never happens).
 
-   In addition, default installed :class:`ProxyHandler` makes sure the requests
-   are handled through the proxy when they are set.
+   In addition, if proxy settings are detected (for example, when a ``*_proxy``
+   environment variable like :envvar:`http_proxy` is set),
+   :class:`ProxyHandler` is default installed and makes sure the requests are
+   handled through the proxy.
 
    The legacy ``urllib.urlopen`` function from Python 2.6 and earlier has been
    discontinued; :func:`urllib.request.urlopen` corresponds to the old
@@ -126,7 +128,8 @@ The :mod:`urllib.request` module defines the following functions:
    subclasses of :class:`BaseHandler` (in which case it must be possible to call
    the constructor without any parameters).  Instances of the following classes
    will be in front of the *handler*\s, unless the *handler*\s contain them,
-   instances of them or subclasses of them: :class:`ProxyHandler`,
+   instances of them or subclasses of them: :class:`ProxyHandler` (if proxy
+   settings are detected),
    :class:`UnknownHandler`, :class:`HTTPHandler`, :class:`HTTPDefaultErrorHandler`,
    :class:`HTTPRedirectHandler`, :class:`FTPHandler`, :class:`FileHandler`,
    :class:`HTTPErrorProcessor`, :class:`DataHandler`.
@@ -256,9 +259,9 @@ The following classes are provided:
    Cause requests to go through a proxy. If *proxies* is given, it must be a
    dictionary mapping protocol names to URLs of proxies. The default is to read the
    list of proxies from the environment variables :envvar:`<protocol>_proxy`.
-   If no proxy environment variables are set, in a Windows environment, proxy
-   settings are obtained from the registry's Internet Settings section and in a
-   Mac OS X environment, proxy information is retrieved from the OS X System
+   If no proxy environment variables are set, then in a Windows environment proxy
+   settings are obtained from the registry's Internet Settings section, and in a
+   Mac OS X environment proxy information is retrieved from the OS X System
    Configuration Framework.
 
    To disable autodetected proxy pass an empty dictionary.

Misc/ACKS

@@ -804,6 +804,7 @@ Kirk McDonald
 Chris McDonough
 Greg McFarlane
 Alan McIntyre
+Jessica McKellar
 Michael McLay
 Brendan McLoughlin
 Mark Mc Mahon