ST-1381 add python3 dependency

Signed-off-by: Matteo Di Carlo <matteo.dicarlo@inaf.it>

images/ska-tango-images-tango-cpp/Dockerfile

@@ -4,7 +4,7 @@
 # binaries.
 #
 ARG CAR_OCI_REGISTRY_HOST
-ARG BUILD_IMAGE="${CAR_OCI_REGISTRY_HOST}/ska-tango-images-tango-dependencies:9.3.5"
+ARG BUILD_IMAGE="${CAR_OCI_REGISTRY_HOST}/ska-tango-images-tango-dependencies:9.3.10"
 ARG BASE_IMAGE="ubuntu:20.04"
 FROM $BUILD_IMAGE as buildenv
 
@@ -20,7 +20,7 @@ RUN apt-get update && \
         git \
         libmariadbclient-dev \
         libmariadbclient-dev-compat \
-        pkg-config python
+        pkg-config python python3
 
 
 # build and install tangoidl