python-backports.functools_lru_cache: avoid collision with python-backports

Regression introduced with backports.functools-lru-cache-1.4.

Fixes #7175.

srcpkgs/python-backports.functools_lru_cache/template

@@ -1,7 +1,7 @@
 # Template file for 'python-backports.functools_lru_cache'
 pkgname=python-backports.functools_lru_cache
 version=1.4
-revision=1
+revision=2
 noarch=yes
 wrksrc="backports.functools_lru_cache-${version}"
 build_style=python2-module
@@ -20,3 +20,7 @@ pre_build() {
 		-e "/setuptools_scm/d" \
 		-e "s/use_scm_version=True,/version=\"${version}\",/"
 }
+post_install() {
+	# namespace provided by python-backports package
+	rm -f ${DESTDIR}/usr/lib/python*/site-packages/backports/__init__.py
+}