use requirements.in + pip-compile

requirements.in

@@ -0,0 +1,12 @@
+# TODO: find a way to pipe these directly into requirements.txt
+#-d https://raw.githubusercontent.com/ska-sa/katsdpdockerbase/master/docker-base-build/base-requirements.txt
+#-d https://raw.githubusercontent.com/ska-sa/katsdpdockerbase/master/docker-base-gpu-build/requirements.txt
+
+astropy
+dask
+numba
+numpy<1.21,>=1.18
+pre-commit
+pytest
+scipy
+typing-extensions

requirements.txt

@@ -1,11 +1,85 @@
 -d https://raw.githubusercontent.com/ska-sa/katsdpdockerbase/master/docker-base-build/base-requirements.txt
 -d https://raw.githubusercontent.com/ska-sa/katsdpdockerbase/master/docker-base-gpu-build/requirements.txt
+#
+# This file is autogenerated by pip-compile with python 3.6
+# To update, run:
+#
+#    pip-compile requirements.in
+#
+astropy==4.1
+    # via -r requirements.in
+attrs==21.4.0
+    # via pytest
+cfgv==3.3.1
+    # via pre-commit
+dask==2021.3.0
+    # via -r requirements.in
+distlib==0.3.4
+    # via virtualenv
+filelock==3.4.1
+    # via virtualenv
+identify==2.4.4
+    # via pre-commit
+importlib-metadata==4.8.3
+    # via
+    #   pluggy
+    #   pre-commit
+    #   pytest
+    #   virtualenv
+importlib-resources==5.2.3
+    # via
+    #   pre-commit
+    #   virtualenv
+iniconfig==1.1.1
+    # via pytest
+llvmlite==0.36.0
+    # via numba
+nodeenv==1.6.0
+    # via pre-commit
+numba==0.53.1
+    # via -r requirements.in
+numpy==1.19.5
+    # via
+    #   -r requirements.in
+    #   astropy
+    #   numba
+    #   scipy
+packaging==21.3
+    # via pytest
+platformdirs==2.4.0
+    # via virtualenv
+pluggy==1.0.0
+    # via pytest
+pre-commit==2.17.0
+    # via -r requirements.in
+py==1.11.0
+    # via pytest
+pyparsing==3.0.8
+    # via packaging
+pytest==7.0.1
+    # via -r requirements.in
+pyyaml==6.0
+    # via
+    #   dask
+    #   pre-commit
+scipy==1.5.4
+    # via -r requirements.in
+six==1.16.0
+    # via virtualenv
+toml==0.10.2
+    # via pre-commit
+tomli==1.2.3
+    # via pytest
+typing-extensions==4.1.1
+    # via
+    #   -r requirements.in
+    #   importlib-metadata
+virtualenv==20.14.1
+    # via pre-commit
+zipp==3.6.0
+    # via
+    #   importlib-metadata
+    #   importlib-resources
 
-astropy
-dask
-numba
-numpy<1.21,>=1.18
-pre-commit==2.9.2
-pytest
-scipy
-typing-extensions
+# The following packages are considered to be unsafe in a requirements file:
+# setuptools