atk package: hotfix #9099 (#9102)

Adds explicit python3 dependency for meson

var/spack/repos/builtin/packages/atk/package.py

@@ -41,6 +41,12 @@ class Atk(Package):
 
     depends_on('meson', type='build', when='@2.28.0:')
     depends_on('glib')
+    # FIXME: this constraint exists because of the meson dependency.
+    # It should not be required to specify it here, but "spack spec atk" will
+    # fail without it.
+    # See: #2632
+    depends_on('python@3:')
+    depends_on('gettext')
     depends_on('pkgconfig', type='build')
     depends_on('gobject-introspection')