added pyfftw to the docker file

ci/docker_images/ubuntu/bionic/Dockerfile

@@ -197,6 +197,15 @@ RUN cd /tmp                                       \
 # clang 6 for hysop build test
 RUN apt-get install -y clang
 
+# pyfftw (with R2R transforms - experimental branch)
+RUN cd /tmp                                      \
+ && git clone https://github.com/drwells/pyFFTW  \
+ && cd pyFFTW                                    \
+ && git checkout r2r-try-two                     \
+ && pip install .                                \
+ && cd -                                         \
+ && rm -Rf /tmp/pyFFTW
+
 # ensure all libraries are known by the runtime linker
 RUN ldconfig