Drop obsolete PYTHON_COMPAT values from some ebuilds

[pacho2]

I get this errors when updating my system:

 *   No supported implementation in PYTHON_COMPAT.
 * 
 * Call stack:
 *                 ebuild.sh, line 609:  Called source '/hdd/portage/local/layman/maggu2810-overlay/app-i18n/ibus/ibus-1.5.15.ebuild'
 *        ibus-1.5.15.ebuild, line  12:  Called inherit 'autotools' 'bash-completion-r1' 'eutils' 'gnome2-utils' 'multilib' 'python-single-r1' 'readme.gentoo-r1' 'vala' 'virtualx'
 *                 ebuild.sh, line 314:  Called __qa_source '/usr/portage/eclass/python-single-r1.eclass'
 *                 ebuild.sh, line 112:  Called source '/usr/portage/eclass/python-single-r1.eclass'
 *   python-single-r1.eclass, line 269:  Called _python_single_set_globals
 *   python-single-r1.eclass, line 209:  Called _python_set_impls
 *    python-utils-r1.eclass, line 156:  Called die
 * The specific snippet of code:
 *   			die "No supported implementation in PYTHON_COMPAT."
 * 
 * If you need support, post the output of `emerge --info '=app-i18n/ibus-1.5.15::maggu2810-overlay'`,
 * the complete build log and the output of `emerge -pqv '=app-i18n/ibus-1.5.15::maggu2810-overlay'`.
 * Working directory: '/usr/lib/python3.8/site-packages'
 * S: '/var/tmp/portage/app-i18n/ibus-1.5.15/work/ibus-1.5.15'
 * ERROR: app-accessibility/caribou-0.4.21::maggu2810-overlay failed (depend phase):
 *   No supported implementation in PYTHON_COMPAT.
 * 
 * Call stack:
 *                ebuild.sh, line 609:  Called source '/hdd/portage/local/layman/maggu2810-overlay/app-accessibility/caribou/caribou-0.4.21.ebuild'
 *    caribou-0.4.21.ebuild, line   9:  Called inherit 'gnome2' 'python-r1'
 *                ebuild.sh, line 314:  Called __qa_source '/usr/portage/eclass/python-r1.eclass'
 *                ebuild.sh, line 112:  Called source '/usr/portage/eclass/python-r1.eclass'
 *         python-r1.eclass, line 260:  Called _python_set_globals
 *         python-r1.eclass, line 199:  Called _python_set_impls
 *   python-utils-r1.eclass, line 156:  Called die
 * The specific snippet of code:
 *   			die "No supported implementation in PYTHON_COMPAT."
 * 
 * If you need support, post the output of `emerge --info '=app-accessibility/caribou-0.4.21::maggu2810-overlay'`,
 * the complete build log and the output of `emerge -pqv '=app-accessibility/caribou-0.4.21::maggu2810-overlay'`.
 * Working directory: '/usr/lib/python3.8/site-packages'
 * S: '/var/tmp/portage/app-accessibility/caribou-0.4.21/work/caribou-0.4.21'

Thanks

[maggu2810]

I moved away from Gentoo, so don't expect a fix from my side.
But I will merge a pull request if you are willing to solve it for you and others.