* Build a PrivateStorage-related Android application
  * Build an app that can interact with magic-folders somehow
    * Build an app that can read magic-folders and download linked files
      * Build an app that runs the Python Tahoe-LAFS implementation on Android
	* Build Tahoe-LAFS & ZKAPAuthorizer for Android
	  * Build Python for Android

	    * Terms
	      * "Build system" is the system where you compile a package.
	      * "Host system" is the system where you run the package.

	    * Try using nix (nixpkgs 3d58e3a31ee55554fe26650bb59db7d6d0e97625 / https://github.com/NixOS/nixpkgs/pull/201734 rebased onto staging) ::

		nix build .#pkgsCross.aarch64-android.python3Minimal

	    * Or, Chaquopy has a build

	  * Build TahoeLAFS/ZKAPAuthorizer dependencies for Android

	    * zfec

	    * ::

		nix build .#pkgsCross.aarch64-android.python3Minimal.pkgs.zfec

	      However, this fails.
	      Building an aarch64-android wheel package fails::

                  running bdist_wheel
                  Traceback (most recent call last):
                    File "/build/wheel-0.37.1-source/nix_run_setup", line 8, in <module>
                      exec(compile(getattr(tokenize, 'open', open)(__file__).read().replace('\\r\\n', '\\n'), __file__, 'exec'))
                    File "setup.py", line 4, in <module>
                      setup(maintainer=u'Alex Grönholm')
                    File "/nix/store/87qbq45psc97az9h5qmn6csfvrj9gl6g-python3.10-bootstrapped-pip-22.2.2/lib/python3.10/site-packages/setuptools/__init__.py", line 87, in setup
                      return distutils.core.setup(**attrs)
                  .
                  .
                  .
                    File "/nix/store/lygssilaq8p1a85pmbnfd7k2yw76kf2k-python3-minimal-3.10.8/lib/python3.10/importlib/metadata/__init__.py", line 171, in load
                      module = import_module(match.group('module'))
                    File "/nix/store/lygssilaq8p1a85pmbnfd7k2yw76kf2k-python3-minimal-3.10.8/lib/python3.10/importlib/__init__.py", line 126, in import_module
                      return _bootstrap._gcd_import(name[level:], package, level)
                  .
                  .
                  .
                    File "/nix/store/87qbq45psc97az9h5qmn6csfvrj9gl6g-python3.10-bootstrapped-pip-22.2.2/lib/python3.10/site-packages/setuptools/command/build_ext.py", line 26, in <module>
                      get_config_var("LDSHARED")
                    File "/nix/store/87qbq45psc97az9h5qmn6csfvrj9gl6g-python3.10-bootstrapped-pip-22.2.2/lib/python3.10/site-packages/setuptools/_distutils/sysconfig.py", line 574, in get_config_var
                      return get_config_vars().get(name)
                    File "/nix/store/87qbq45psc97az9h5qmn6csfvrj9gl6g-python3.10-bootstrapped-pip-22.2.2/lib/python3.10/site-packages/setuptools/_distutils/sysconfig.py", line 553, in get_config_vars
                      _config_vars = sysconfig.get_config_vars().copy()
                    File "/nix/store/lygssilaq8p1a85pmbnfd7k2yw76kf2k-python3-minimal-3.10.8/lib/python3.10/sysconfig.py", line 615, in get_config_vars
                      _init_posix(_CONFIG_VARS)
                    File "/nix/store/lygssilaq8p1a85pmbnfd7k2yw76kf2k-python3-minimal-3.10.8/lib/python3.10/sysconfig.py", line 477, in _init_posix
                      _temp = __import__(name, globals(), locals(), ['build_time_vars'], 0)
                  ModuleNotFoundError: No module named '_sysconfigdata__linux_aarch64-linux-android'

	      ``_sysconfigdata__linux_aarch64-linux-android`` is meant to hold information about the host platform for the software to be built.
	      CPython doesn't have a good cross-compilation system.
	      It will guess a sysconfidata module name to import or use a value given by _PYTHON_SYSCONFIGDATA_NAME.
	      nixpkgs defines a value for _PYTHON_SYSCONFIGDATA_NAME.
	      In this case it sets it to ``_sysconfigdata__linux_aarch64-linux-android``.
	      The CPython that is running is the "Python for build" interpreter -
	      the interpreter that is able to run on the build system.
	      It is searching for the sysconfigdata for the "Python for host" interpreter -
	      the interpreter that is able to run on the system where the package being built will be used.
	      The "Python for build" interpreter has ``site-packages/_sysconfigdata__linux_x86_64-linux-gnu.py``
	      which is a symlink to ``_sysconfigdata__linux_x86_64-linux-gnu.py`
	      which exists
	      and contains information about the build system.
	      The pkgsCross.aarch64-android.python3Minimal.pkgs.zfec derivation has PYTHONPATH set in its environment.
	      The value (split up for readability) is

	        * /nix/store/53afd480zidx2p9j9c7dsgckjgfk66h1-python3-minimal-aarch64-unknown-linux-android-3.10.8/lib/python3.10/site-packages
		* /nix/store/azdg3l16q2d03g8drgr94bg1069mfzpq-python3.10-bootstrapped-pip-22.2.2/lib/python3.10/site-packages
		* /nix/store/spk2md1jgwrg6id10j1rl9448s4naa94-python3.10-setuptools-65.3.0/lib/python3.10/site-packages
		* /nix/store/537cvh8mqdaglc0an8ndmzszllh1lwac-python3-minimal-3.10.8/lib/python3.10/site-packages

	      The first entry is a directory which contains ``_sysconfigdata__linux_.py``
	      which is a symlink to ``../_sysconfigdata__linux_.py``
	      which exists
	      and contains information about the host system.

	      The ``_sysconfigdata_*`` file is

	      * named by ``sysconfig._get_sysconfigdata_name``
	      * and written by ``sysconfig._generate_posix_vars``
	      * which is called by ``sysconfig._main``
	      * which is invoked by the ``pybuilddir.txt`` Makefile target
	      * which is depended on by the ``sharedmods`` Makefile target
	      * which is depended on by the ``build_all`` and ``sharedinstall`` Makefile targets
	      * ``build_all`` is the default Make target
	      * nixpkgs python3Minimal expression defines a postFixup hook
		* ``sysconfigdataHook`` ::

                    sysconfigdataHook() {
                      if [ "$1" = '${placeholder "out"}' ]; then
                        export _PYTHON_HOST_PLATFORM='${pythonHostPlatform}'
                        export _PYTHON_SYSCONFIGDATA_NAME='${pythonSysconfigdataName}'
                      fi
                    }

                    addEnvHooks "$hostOffset" sysconfigdataHook

		* This runs after the fixup phase (very late in the build) and sets a couple environment variables pointing at the correct *host* Python sysconfig data.
		* On a native build
		  * buildPhase started
		  * lots of core compiling
		  * ``LD_LIBRARY_PATH=/build/Python-3.10.8 ./python -E -S -m sysconfig --generate-posix-vars``
		  * lots of extension module compiling
		  * ``_sysconfigdata__linux_x86_64-linux-gnu.py`` generated/written

		* On an aarch64-multiplatform build
		  * buildPhase started
		  * lots of core compiling
		  * ``_PYTHON_PROJECT_BASE=/build/Python-3.10.8 _PYTHON_HOST_PLATFORM=linux-aarch64 PYTHONPATH=./Lib _PYTHON_SYSCONFIGDATA_NAME=_sysconfigdata__linux_aarch64-linux-gnu python -S -m sysconfig --generate-posix-vars``
		  * lots of extension module compiling
		  * ``_sysconfigdata__linux_aarch64-linux-gnu.py'`` generated/written

		* On an aarch64-android build
		  * buildPhase started
		  * lots of core compiling
		  * ``_PYTHON_PROJECT_BASE=/build/Python-3.10.8 _PYTHON_HOST_PLATFORM=linux-aarch64 PYTHONPATH=./Lib _PYTHON_SYSCONFIGDATA_NAME=_sysconfigdata__linux_ python -S -m sysconfig --generate-posix-vars``

		    * Uh oh.
		      ``_sysconfigdata__linux_``
		      Why?

		      * We expect to see ``_sysconfigdata__linux_aarch64-linux-android``

			* This means the "abi flags" are ""
			  The "platform" is "linux" (questionable...)
			  The "multiarch" is "aarch64-linux-android" (is that coherent?)

			* The exact string might not really matter, we just need it to agree.
			  Where is the multiarch suffix going?


		      * The nixpkgs expression does not result in this string
			(by inspection with builtins.trace)



	    * python-cryptography
	    * python-challenge-bypass-ristretto

	* Integrate a Python Tahoe-LAFS runtime with a GUI

	  * Build a GUI