GH-127236: `pathname2url()`: generate RFC 1738 URL for absolute POSIX path (#127194)

When handed an absolute Windows path such as `C:\foo` or `//server/share`,
the `urllib.request.pathname2url()` function returns a URL with an
authority section, such as `///C:/foo` or `//server/share` (or before
GH-126205, `////server/share`). Only the `file:` prefix is omitted.

But when handed an absolute POSIX path such as `/etc/hosts`, or a Windows
path of the same form (rooted but lacking a drive), the function returns a
URL without an authority section, such as `/etc/hosts`.

This patch corrects the discrepancy by adding a `//` prefix before
drive-less, rooted paths when generating URLs.

1 files changed, 6 insertions, 4 deletions

diff --git a/Doc/library/urllib.request.rst b/Doc/library/urllib.request.rst
index 9055556..3c07dc4 100644
--- a/Doc/library/urllib.request.rst
+++ b/Doc/library/urllib.request.rst
@@ -159,12 +159,14 @@ The :mod:`urllib.request` module defines the following functions:
       'file:///C:/Program%20Files'
 
    .. versionchanged:: 3.14
-      Windows drive letters are no longer converted to uppercase.
+      Paths beginning with a slash are converted to URLs with authority
+      sections. For example, the path ``/etc/hosts`` is converted to
+      the URL ``///etc/hosts``.
 
    .. versionchanged:: 3.14
-      On Windows, ``:`` characters not following a drive letter are quoted. In
-      previous versions, :exc:`OSError` was raised if a colon character was
-      found in any position other than the second character.
+      Windows drive letters are no longer converted to uppercase, and ``:``
+      characters not following a drive letter no longer cause an
+      :exc:`OSError` exception to be raised on Windows.
 
 
 .. function:: url2pathname(url)