predownload registry JSON + install system deps in early layer

Dockerfile

@@ -1,16 +1,32 @@
+# FIXME: when using the torch 2.0.1 image, we get an error
+#   OSError: /lib/x86_64-linux-gnu/libgobject-2.0.so.0: undefined symbol: ffi_type_uint32, version LIBFFI_BASE_7.0
+# The error is fixed by
+#   LD_PRELOAD=/usr/lib/x86_64-linux-gnu/libffi.so.7
+
 FROM pytorch/pytorch:2.0.0-cuda11.7-cudnn8-runtime
-WORKDIR /opt/wsinfer
-COPY . .
+ARG DEBIAN_FRONTEND="noninteractive"
+ENV TZ=Etc/UTC
+
+# Install system dependencies.
 RUN apt-get update \
     && apt-get install -y --no-install-recommends gcc g++ git libopenslide0 \
-    && python -m pip install --no-cache-dir --editable . \
     && rm -rf /var/lib/apt/lists/*
+
+# Install wsinfer.
+WORKDIR /opt/wsinfer
+COPY . .
+RUN python -m pip install --no-cache-dir --editable .
+
 # Use a writable directory for downloading model weights. Default is ~/.cache, which is
 # not guaranteed to be writable in a Docker container.
 ENV TORCH_HOME=/var/lib/wsinfer
 RUN mkdir -p "$TORCH_HOME" \
     && chmod 777 "$TORCH_HOME" \
     && chmod a+s "$TORCH_HOME"
+
+# Test that the program runs (and also download the registry JSON file).
+RUN wsinfer --help
+
 WORKDIR /work
 ENTRYPOINT ["wsinfer"]
 CMD ["--help"]