Install dirmngr dependency

Author: alessfg

tests/dockerfiles/Dockerfile.debian-stretch

@@ -12,6 +12,7 @@ RUN apt-get update -y && apt-get install -y --no-install-recommends \
     apt-transport-https \
     curl \
     gnupg2 \
+    dirmngr \
  && rm -rf /var/lib/apt/lists/*
 
 RUN pip install --upgrade setuptools && pip install ansible