edit tool is [pathlib_edit.py][1]

Two tweaks in repository.py were done manually.

[1]: https://gist.github.com/dckc/40c8caf4c1dc0027ac0d3b1fdbb251d2

  - 4 space indentation
  - 79 characater line length

While get_data(), like import, is actually runtime I/O,
we consider access to design-time constants as if it
were access to any other static data (string, integer, ...).

  - no powerful imports: os, subprocess, ...
    - copyfileobj is powerless: file access is passed in
    - PurePosixPath for syntax manipulation is also powerless
  - use PathExt rather than strings for access to files
    - allfiles KLUDGE: navigation thru absolute paths
    - PathTFix.__truediv__ Self type work-around (for p / sub)
    - cast .iterdir() result because our Self type work-around
      isn't smart enough
    - open() -> path.open()
  - pass urlopen, subprocess, random to Distfile as a distfile.Access
    - simplify, export UrlopenFn: always returns BinaryIO
    - util.RunCommand class represents subprocess interface
    - declare type for util.diff mkPopen arg
  - Distfile.__init__() static types (e.g. Hash) help with refactoring
    - complete static types for all Distfile methods
  - log.warning() is only declared to take a str. hm.

  - DiffCreator gets subprocess
  - BuildDirectory gets platform
  - FileHandle etc. get an Access (subprocess etc.)
    - add check_output to RunCommand interface
  - Builder interface common to HostBuilder and TargetBuilder
  - refactor allpath KLUDGE using PathExt.platform() and
    config.config_path_fn
    - use single-assignment idiom for tar vs bsdtar
  - prune resource_directory
    - restore DIR_RESOURCES but only as a PurePath for use with check_call()
  - Distfile needs a RandomT
  - never mind PathTFix generic Self
    It didn't work -- turned into Any -- and hid a few type errors.

  - static types rather than **kwargs for op_distfile etc.
  - NamedTuple rather than dict for deferred package info
  - types for version (sometimes a class), checksum (always str)
    - class AnyVersion reifies type common to SimpleVersion, FullVersion
  - master_sites, patches are Set[str], not List[str]
  - move `build_depends = set()` to else branch to help mypy
  - clarify builder.Access name
  - prune more resource_directory dead code

  - two blank lines before class, def
  - 4 space indent
  - 79 character line limit

  - unused: SimpleVersion, lib_depends, files
  - two lines before class
  - spaces around / and after :
  - }); formatting

run with `py.test`, for example

found through unit testing

add __init__.py for use with pkgutil.get_data

perhaps a bit of a kludge? but a harmless one

and move test_suite into `src` dir