PEP8 says that:
"Comparisons to singletons like None should always be done with is or
is not, never the equality operators."
glib uses a mix of "== None" and "is None". This patch changes all
cases to the latter.
glib installs a gdb helper file named `glib.py`.
Then the "hook" file updates `sys.path` and does `import glib`.
This will fail if glib has already been imported into gdb, say
using `from gi.repository import GLib`. This is due to a namespace clash.
One fix would be to rename the gdb helper files to not clash with
other Python modules. This should be done for all such helper files.
https://bugzilla.gnome.org/show_bug.cgi?id=760186
