gnu: Add python-pygobject-3.50.

* gnu/packages/glib.scm (python-pygobject-3.50): New variable.
* gnu/packages/gnome.scm (glade3, blueprint-compiler, libsecret)
(orca)[native-inputs]: Replace python-pygobject with python-pygobject-3.50.
(libpeas, libpeas-2, totem, rhythmbox, network-manager, gedit, endeavour)
(gnome-builder)[inputs]: Likewise.
* gnu/packages/gimp.scm (gimp-3)[inputs]: Likewise.
* gnu/packages/ibus.scm (ibus)[inputs]: Likewise.

gnu/packages/gimp.scm

@@ -450,7 +450,7 @@ that is extensible via a plugin system.")
                        libxmu
                        libxt
                        python
-                       python-pygobject
+                       python-pygobject-3.50
                        gjs
                        libxslt
                        xdg-utils)))

gnu/packages/glib.scm

@@ -1100,6 +1100,20 @@ useful for C++.")
      '((upstream-name . "pygobject")))
     (license license:lgpl2.1+)))
 
+(define-public python-pygobject-3.50
+  (package
+    (inherit python-pygobject)
+    (version "3.50.2")
+    (source
+     (origin
+       (method url-fetch)
+       (uri (string-append "mirror://gnome/sources/pygobject/"
+                           (version-major+minor version)
+                           "/pygobject-" version ".tar.gz"))
+       (sha256
+        (base32
+         "1zx7jz9s1qnn52k3kzbz5ykffr9pm3c8hvpwzm4vcz5pm9hbirpc"))))))
+
 (define-public perl-glib
   (package
     (name "perl-glib")

gnu/packages/gnome.scm

@@ -3124,7 +3124,7 @@ some form of information without getting in the user's way.")
      (list gtk+
            glade3
            python
-           python-pygobject))
+           python-pygobject-3.50))
     (native-inputs
      (list pkg-config
            gettext-minimal
@@ -3171,7 +3171,7 @@ API.")
            ;; lua-5.1
            ;; lua5.1-lgi
            python
-           python-pygobject))))
+           python-pygobject-3.50))))
 
 (define-public gtkglext
   (package
@@ -3264,7 +3264,7 @@ API add-ons to make GTK+ widgets OpenGL-capable.")
            itstool
            libxslt                      ;for xsltproc
            python
-           python-pygobject
+           python-pygobject-3.50
            pkg-config
            xorg-server-for-tests))
     (home-page "https://glade.gnome.org")
@@ -3322,7 +3322,7 @@ the GNOME desktop environment.")
     (native-inputs (list gtk
                          libadwaita
                          python
-                         python-pygobject
+                         python-pygobject-3.50
                          xorg-server-for-tests))
     (inputs (list python))
     (synopsis "Template markup language")
@@ -5235,7 +5235,7 @@ and the GLib main loop, to integrate well with GNOME applications.")
            pkg-config
            python
            python-dbus
-           python-pygobject
+           python-pygobject-3.50
            vala))
     (propagated-inputs
      (list glib libgcrypt))             ;required by libsecret-1.pc
@@ -6679,7 +6679,7 @@ discovery protocols.")
            libxtst
            libxxf86vm
            python
-           python-pygobject
+           python-pygobject-3.50
            totem-pl-parser
            vala
            xorgproto))
@@ -6805,7 +6805,7 @@ which can read a large number of file formats.")
            lirc
            pango
            python
-           python-pygobject
+           python-pygobject-3.50
            tdb
            totem-pl-parser))
     (home-page "https://wiki.gnome.org/Apps/Rhythmbox")
@@ -7816,7 +7816,7 @@ javascript engine and the GObject introspection framework.")
            libpeas
            libsoup
            python
-           python-pygobject
+           python-pygobject-3.50
            tepl))
     (home-page "https://wiki.gnome.org/Apps/Gedit")
     (synopsis "GNOME text editor")
@@ -8392,7 +8392,7 @@ users.")
            perl
            pkg-config
            python-dbus
-           python-pygobject
+           python-pygobject-3.50
            python-wrapper
            vala))
     (inputs
@@ -10699,7 +10699,7 @@ desktop.  It supports multiple calendars, month, week and year view.")
            libical
            libpeas
            libportal
-           python-pygobject
+           python-pygobject-3.50
            gnome-online-accounts
            gsettings-desktop-schemas))
     (propagated-inputs
@@ -11441,7 +11441,7 @@ accessibility infrastructure.")
            `(,liblouis "python")
            procps                       ; for pgrep
            python
-           python-pygobject
+           python-pygobject-3.50
            python-pyatspi
            speech-dispatcher
            xkbcomp))
@@ -13544,7 +13544,7 @@ GtkTextView widgets.")
            llvm
            libostree
            python
-           python-pygobject
+           python-pygobject-3.50
            sysprof
            template-glib
            vte

gnu/packages/ibus.scm

@@ -277,7 +277,7 @@ may also simplify input method development.")
                        pango
                        python
                        python-dbus
-                       python-pygobject)))
+                       python-pygobject-3.50)))
     (native-search-paths
      (cons (search-path-specification
             (variable "GUIX_GTK3_IM_MODULE_FILE")