updated ubuntu (#229)

* updated ubuntu

* older version but doesn't deprecate until 2021

* install gpg-agent

docker/Dockerfile

@@ -1,4 +1,4 @@
-FROM ubuntu:17.10
+FROM ubuntu:18.04
 
 # https://github.com/phusion/baseimage-docker/issues/58
 ARG DEBIAN_FRONTEND=noninteractive
@@ -21,6 +21,7 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
   g++ \
   gfortran \
   git-core \
+  gpg-agent \
   libblas-dev \
   libffi-dev \
   liblapack-dev \
@@ -47,7 +48,7 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
 
 # install mssql drivers https://msdn.microsoft.com/en-us/library/hh568454(v=sql.110).aspx
 RUN curl https://packages.microsoft.com/keys/microsoft.asc | apt-key add - \
-  && curl https://packages.microsoft.com/config/ubuntu/17.10/prod.list > /etc/apt/sources.list.d/mssql-release.list
+  && curl https://packages.microsoft.com/config/ubuntu/18.04/prod.list > /etc/apt/sources.list.d/mssql-release.list
 RUN apt-get update && ACCEPT_EULA=Y apt-get install -y --no-install-recommends \
   msodbcsql17 \
   mssql-tools \