lib.ec.SSHClientInternal|SSHClientCmd: Own .py

Move the code of SSHClientInternal and SSCClientCmd into lib.ec.ssh,
as "Paramiko" and "Exec", respectively. This makes the class layout
a little more modular, and along the way fixes a bug where
SSHClientInternal could be instantiated but was unusable (if the
Paramiko is not installed).

Signed-off-by: Jan Lindemann <jan@janware.com>

src/python/jw/pkg/lib/ec/ssh/Paramiko.py

@@ -0,0 +1,57 @@
+from __future__ import annotations
+
+from typing import TYPE_CHECKING
+
+import paramiko # type: ignore # error: Library stubs not installed for "paramiko"
+import shlex
+
+from ...log import *
+from ...ExecContext import Result
+from ..SSHClient import SSHClient as Base
+
+class Paramiko(Base): # export
+
+    def __init__(self, *args, **kwargs) -> None:
+        super().__init__(*args, **kwargs)
+        self.__timeout: float|None = None # Untested
+        self.___ssh: Any|None = None
+
+    def __ssh_connect(self):
+        ret = paramiko.SSHClient()
+        ret.set_missing_host_key_policy(paramiko.AutoAddPolicy())
+        try:
+            ret.connect(
+                hostname=self.hostname,
+                username=self.username,
+                allow_agent=True
+            )
+        except Exception as e:
+            log(ERR, f'Failed to connect to {self.hostname} with key file {path_to_key} ({str(e)})')
+            raise
+        s = ret.get_transport().open_session()
+        # set up the agent request handler to handle agent requests from the server
+        paramiko.agent.AgentRequestHandler(s)
+        return ret
+
+    @property
+    def __ssh(self):
+        if self.___ssh is None:
+            self.___ssh = self.__ssh_connect()
+        return self.___ssh
+
+    @property
+    def __scp(self):
+        return SCPClient(self.__ssh.get_transport())
+
+    async def _run_ssh(self, cmd: list[str], cmd_input: str|None) -> Result:
+        try:
+            stdin, stdout, stderr = self.__ssh.exec_command(shlex.join(cmd), timeout=self.__timeout)
+        except Exception as e:
+            log(ERR, f'Command failed for {self.uri}: "{shlex.join(cmd)}"')
+            raise
+        if cmd_input is not None:
+            stdin.write(cmd_input)
+        exit_status = stdout.channel.recv_exit_status()
+        return Result(stdout.read(), stderr.read(), exit_status)
+
+