Update 'PKGBUILD'

PKGBUILD

@@ -23,7 +23,7 @@ build() {
 package() {
 	install -Dm644 LICENSE "$pkgdir/usr/share/licenses/$pkgname/LICENSE"
 	cd "$srcdir/$pkgname"
-	mkdir usr;
+	mkdir -p usr;
 	export PYTHONUSERBASE=$pkgdir/usr;
 	python2 setup.py install --user;
 }