Removed python-graphviz

Dockerfile

@@ -5,7 +5,7 @@ WORKDIR /opt/netbox
 ARG BRANCH=master
 ARG URL=https://github.com/digitalocean/netbox.git
 RUN git clone --depth 1 $URL -b $BRANCH .  && \
-    apt-get update -qq && apt-get install -y libldap2-dev libsasl2-dev libssl-dev graphviz python-pygraphviz && \
+    apt-get update -qq && apt-get install -y libldap2-dev libsasl2-dev libssl-dev graphviz && \
 	pip install gunicorn==17.5 && \
 	pip install django-auth-ldap && \
     pip install -r requirements.txt