bpo-43137: webbrowser: Prefer gio open over gvfs-open

gvfs-open(1) was superseded by gio(1) in 2015, and removed from GNOME
releases in 2018. Debian and its derivatives like Ubuntu currently still
have a compatibility shim for gvfs-open, but we plan to remove it.

webbrowser prefers xdg-settings and xdg-open over gvfs-open, so this
will only have any practical effect on systems where the xdg-utils
package is not installed.

Note that we don't check for GNOME_DESKTOP_SESSION_ID before using gio.
gio does the right thing on any desktop environment that follows
freedesktop.org specifications, similar to xdg-settings, so it's
unnecessary to guard in this way. GNOME_DESKTOP_SESSION_ID was deprecated
in 2008 and removed from upstream gnome-session in 2018 (it's still
present in Debian/Ubuntu for backward compatibility, but probably
shouldn't be). The replacement way to detect a desktop environment is
the XDG_CURRENT_DESKTOP environment variable, which is a colon-separated
sequence where the first item is the current desktop environment and the
second and subsequent items (if present) are other desktop environments
that it resembles or is based on.

Resolves: https://bugs.python.org/issue43137
Signed-off-by: Simon McVittie <[email protected]>

Author: smcv

Lib/webbrowser.py

@@ -462,11 +462,16 @@ def register_X_browsers():
     if shutil.which("xdg-open"):
         register("xdg-open", None, BackgroundBrowser("xdg-open"))
 
-    # The default GNOME3 browser
+    # Opens an appropriate browser for the URL scheme according to
+    # freedesktop.org settings (GNOME, KDE, XFCE, etc.)
+    if shutil.which("gio"):
+        register("gio", None, BackgroundBrowser(["gio", "open", "--", "%s"]))
+
+    # Equivalent of gio open before 2015
     if "GNOME_DESKTOP_SESSION_ID" in os.environ and shutil.which("gvfs-open"):
         register("gvfs-open", None, BackgroundBrowser("gvfs-open"))
 
-    # The default GNOME browser
+    # The default GNOME browser before 2008
     if "GNOME_DESKTOP_SESSION_ID" in os.environ and shutil.which("gnome-open"):
         register("gnome-open", None, BackgroundBrowser("gnome-open"))