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/util.py

@@ -69,9 +69,9 @@ async def run_cmd(
         if code == 0:
             return
         if (throw or verbose):
-            msg = f'Command returned error {code}: {pretty_cmd(args, wd)}: '
+            msg = f'Command returned error {code}: {pretty_cmd(args, wd)}'
             if stderr:
-                msg += stderr.strip()
+                msg += ': ' + stderr.strip()
             if throw:
                 raise RuntimeError(msg)
 
@@ -279,21 +279,9 @@ async def run_askpass(askpass_env: list[str], key: AskpassKey, host: str|None=No
     return None
 
 async def run_sudo(cmd: list[str], mod_env: dict[str, str] = {}, opts: list[str]=[], interactive: bool=True, verbose=True):
-    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 interactive:
-        cmd_input = "mode:interactive"
-    return await run_cmd(cmdline, throw=True, verbose=verbose, env=env, cmd_input=cmd_input)
+    from .ec.Local import Local
+    ec = Local()
+    return await ec.sudo(cmd, mod_env, opts, interactive, verbose)
 
 async def get_username(args: Namespace|None=None, url: str|None=None, askpass_env: list[str]=[]) -> str: # export
     url_user = None if url is None else urlparse(url).username