ssh: better error reporting on SshSession errors

plumbum/commands/processes.py

@@ -127,8 +127,9 @@ class ProcessExecutionError(EnvironmentError):
     well as the command line used to create the process (``argv``)
     """
 
-    def __init__(self, argv, retcode, stdout, stderr):
+    def __init__(self, argv, retcode, stdout, stderr, message=None):
         Exception.__init__(self, argv, retcode, stdout, stderr)
+        self.message = message
         self.argv = argv
         self.retcode = retcode
         if six.PY3 and isinstance(stdout, six.bytes):
@@ -139,11 +140,18 @@ def __init__(self, argv, retcode, stdout, stderr):
         self.stderr = stderr
 
     def __str__(self):
+        # avoid an import cycle
         from plumbum.commands.base import shquote_list
         stdout =      "\n              | ".join(str(self.stdout).splitlines())
         stderr =      "\n              | ".join(str(self.stderr).splitlines())
         cmd = " ".join(shquote_list(self.argv))
-        lines = ["Unexpected exit code: ", str(self.retcode)]
+        lines = []
+        if self.message:
+            lines = [
+                self.message,
+                      "\nReturn code:  | ", str(self.retcode)]
+        else:
+            lines = ["Unexpected exit code: ", str(self.retcode)]
         cmd =         "\n              | ".join(cmd.splitlines())
         lines +=     ["\nCommand line: | ", cmd]
         if stdout:

plumbum/machines/session.py

@@ -3,6 +3,7 @@
 import logging
 import threading
 from plumbum.commands import BaseCommand, run_proc
+from plumbum.commands.processes import ProcessExecutionError
 from plumbum.lib import six
 from plumbum.machines.base import PopenAddons
 
@@ -13,7 +14,7 @@ class ShellSessionError(Exception):
     pass
 
 
-class SSHCommsError(EOFError):
+class SSHCommsError(ProcessExecutionError, EOFError):
     """Raises when the communication channel can't be created on the
     remote host or it times out."""
 
@@ -124,16 +125,30 @@ def communicate(self, input=None):
 
                 self.proc.poll()
                 returncode = self.proc.returncode
+                stdout = six.b("").join(stdout).decode(self.custom_encoding, "ignore")
+                stderr = six.b("").join(stderr).decode(self.custom_encoding, "ignore")
+                argv = self.argv.decode(self.custom_encoding, "ignore").split(";")[:1]
+
                 if returncode == 5:
                     raise IncorrectLogin(
-                        "Incorrect username or password provided")
+                        argv, returncode, stdout, stderr,
+                        message="Incorrect username or password provided")
                 elif returncode == 6:
                     raise HostPublicKeyUnknown(
-                        "The authenticity of the host can't be established")
-                msg = "No communication channel detected. Does the remote exist?"
-                msgerr = "No stderr result detected. Does the remote have Bash as the default shell?"
-                raise SSHCommsChannel2Error(
-                    msgerr) if name == "2" else SSHCommsError(msg)
+                        argv, returncode, stdout, stderr,
+                        message="The authenticity of the host can't be established")
+                elif returncode != 0:
+                    raise SSHCommsError(
+                        argv, returncode, stdout, stderr,
+                        message="SSH communication failed")
+                elif name == "2":
+                    raise SSHCommsChannel2Error(
+                        argv, returncode, stdout, stderr,
+                        message="No stderr result detected. Does the remote have Bash as the default shell?")
+                else:
+                    raise SSHCommsError(
+                        argv, returncode, stdout, stderr,
+                        message="No communication channel detected. Does the remote exist?")
             if not line:
                 del sources[i]
             else: