proxysql: bundled libinjection needs Python 2

So far, it "worked" because Python 2 was found on the system.
Not the case anymore in our Debian 11 test nodes.

component/proxysql/buildout.cfg

@@ -15,6 +15,8 @@ extends =
   ../patch/buildout.cfg
   ../pcre/buildout.cfg
   ../perl/buildout.cfg
+# https://github.com/libinjection/libinjection/issues/4
+  ../python-2.7/buildout.cfg
 
 parts =
   proxysql
@@ -34,7 +36,7 @@ post-install =
   install -Dt %(location)s/bin %(make-targets)s
 environment =
   PKG_CONFIG_PATH=${openssl:location}/lib/pkgconfig:${gnutls:location}/lib/pkgconfig:${libgcrypt:location}/lib/pkgconfig:${zlib:location}/lib/pkgconfig:${pcre:location}/lib/pkgconfig
-  PATH=${m4:location}/bin:${libtool:location}/bin:${libgcrypt:location}/bin:${curl:location}/bin:${perl:location}/bin:${pkgconfig:location}/bin:${bzip2:location}/bin:${autoconf:location}/bin:${git:location}/bin:${automake:location}/bin:${patch:location}/bin:${cmake-3.18:location}/bin:%(PATH)s
+  PATH=${m4:location}/bin:${libtool:location}/bin:${libgcrypt:location}/bin:${curl:location}/bin:${perl:location}/bin:${pkgconfig:location}/bin:${bzip2:location}/bin:${autoconf:location}/bin:${git:location}/bin:${automake:location}/bin:${patch:location}/bin:${cmake-3.18:location}/bin:%(PATH)s:${python2.7:location}/bin
   CXXFLAGS=-I${openssl:location}/include -I${gnutls:location}/include -I${zlib:location}/include
   CFLAGS=-I${gnutls:location}/include
   LDFLAGS=-L${openssl:location}/lib -Wl,-rpath -Wl,${gnutls:location}/lib -L${gnutls:location}/lib -Wl,-rpath=${curl:location}/lib -L${libtool:location}/lib -L${zlib:location}/lib -Wl,-rpath -Wl,${zlib:location}/lib -L${curl:location}/lib -L${pcre:location}/lib -L${jemalloc:location}/lib -L${libmicrohttpd:location}/lib