python3-attrdict3: add missing run-time dependencies

Add missing RDEPENDS for this package.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Signed-off-by: Khem Raj <raj.khem@gmail.com>

meta-python/recipes-devtools/python3-attrdict3/python3-attrdict3_2.0.2.bb

@@ -10,3 +10,5 @@ SRC_URI[sha256sum] = "004c171ca1120cc1755701db99d7fa4944afb1e68950434efdaa542513
 inherit pypi setuptools3
 
 BBCLASSEXTEND = "native"
+
+RDEPENDS:${PN} += "python3-six"