anchor.diff:      /src/legacypipe/py/{legacypipe,legacyzpts}
   
   # update legacypipe
  -RUN cd /src/legacypipe && git pull && git checkout preburn-lslga && git describe && echo 1 && \
  +RUN cd /src/legacypipe && git pull && git describe && \
     python    -m compileall /src/legacypipe/py/{legacypipe,legacyzpts} && \
     python -O -m compileall /src/legacypipe/py/{legacypipe,legacyzpts}
   
  
positive.code: 
  # Pip installs -- built from source
  RUN pip --no-cache-dir install photutils
  #RUN pip --no-cache-dir install fitsio==1.0.5
  RUN pip --no-cache-dir install git+https://github.com/esheldon/fitsio.git@v1.0.6
  # HACK -- update fitsio version number string
  RUN sed -i -e s/1.0.5/1.0.6/g /opt/conda/lib/python3.7/site-packages/fitsio/__init__.py
  
  RUN wget -nv https://www.mpich.org/static/downloads/3.3/mpich-3.3.tar.gz \
      && tar xvzf mpich-3.3.tar.gz \
      && cd mpich-3.3 \
      && ./configure \
      && make -j4 \
      && make install \
      && make clean \
      && cd .. && rm -Rf mpich-3.3
  # defaults to installing in /usr/local
  
  # mpi4py / mpicc can't handle -ax=knl
  ENV CFLAGS -O3 -g -fPIC -std=gnu99 -pthread
  
  RUN wget -nv https://bitbucket.org/mpi4py/mpi4py/downloads/mpi4py-3.0.3.tar.gz \
           && tar xvzf mpi4py-3.0.3.tar.gz \
           && cd mpi4py-3.0.3 \
           && python setup.py build \
           && python setup.py install \
           && cd .. && rm -Rf mpi4py-3.0.3 mpi4py-3.0.3.tar.gz
  
  ENV CFLAGS -O3 -g -fPIC -std=gnu99 -pthread -x=haswell -ax=knl
  
  RUN /sbin/ldconfig
  
  
negative.code:     && make clean \
      && (cd && PYTHONPATH=/usr/local/lib/python python3 -c "import astrometry; print(astrometry.__version__)")
  
  # Pip installs -- binary.  We need cython for the tractor.
  RUN for x in \
      setuptools \
      wheel \
      psycopg2-binary \
      matplotlib \
      astropy \
      zmq \
      cython \
      ; do pip --no-cache-dir install $x; done
  
  # The Tractor
  RUN git clone http://github.com/dstndstn/tractor.git tractor \
      && cd tractor \
  