Add curl to the image

Dockerfile

@@ -8,6 +8,7 @@ ADD ./packer /usr/local/bin
 RUN apt-get update && apt-get install --no-install-recommends -y \
     git \
     ssh \
+    curl \
  && rm -rf /var/lib/apt/lists/*
 RUN pip install --no-cache-dir --upgrade pip \
  && pip install --no-cache-dir \