lib.Distro, ExecContext: Add classes, refactor lib.distro

The code below lib.distro, as left behind by the previous commit, is geared towards being directly used as a command-line API. This commit introduces the abstract base class Distro, a proxy for distribution-specific interactions. The proxy abstracts distro specifics into an API with proper method prototypes, not argparse.Namespace contents, and can thus be more easily driven by arbitrary code.
The Distro class is initialized with a member variable of type ExecContext, another new class introduced by this commit. It is designed to abstract the communication channel to the distribution instance.  Currently only one specialization exists, Local, which interacts with the distribution and root file system it is running in, but is planned to be subclassed to support interaction via SSH, serial, chroot, or chains thereof.
Signed-off-by: Jan Lindemann <jan@janware.com>

src/python/jw/pkg/lib/ec/Local.py

@@ -0,0 +1,29 @@
+# -*- coding: utf-8 -*-
+
+import os
+
+from ..util import run_cmd
+from ..ExecContext import ExecContext as Base
+from ..ExecContext import Result
+
+class Local(Base):
+
+    async def _run(self, *args, **kwargs) -> Result:
+        return await run_cmd(*args, **kwargs)
+
+    async def _sudo(self, cmd: list[str], mod_env: dict[str, str] = {}, opts: list[str]=[], verbose=True) -> Result:
+        env: dict[str, str]|None = None
+        cmd_input: str|None = None
+        if mod_env:
+            env = os.environ.copy()
+            env.update(mod_env)
+        cmdline = []
+        if os.getuid() != 0:
+            cmdline.append('/usr/bin/sudo')
+            if env is not None:
+                cmdline.append('--preserve-env=' + ','.join(mod_env.keys()))
+            cmdline.extend(opts)
+        cmdline.extend(cmd)
+        if self.interactive:
+            cmd_input = "mode:interactive"
+        return await self._run(cmdline, throw=True, verbose=verbose, env=env, cmd_input=cmd_input)

src/python/jw/pkg/lib/ec/Makefile

@@ -0,0 +1,4 @@
+TOPDIR = ../../../../../..
+
+include $(TOPDIR)/make/proj.mk
+include $(JWBDIR)/make/py-mod.mk