python-lxml: add missing python3 dependency

srcpkgs/python-lxml/template

@@ -1,7 +1,7 @@
 # Template file for 'python-lxml'
 pkgname=python-lxml
 version=4.6.4
-revision=1
+revision=2
 wrksrc="lxml-lxml-${version}"
 build_style=python-module
 make_build_args="--with-cython"
@@ -28,6 +28,7 @@ post_install() {
 
 python3-lxml_package() {
 	short_desc="${short_desc/Python2/Python3}"
+	depends="python3"
 	pkg_install() {
 		vmove usr/lib/python3*
 		vlicense LICENSES.txt