Remove now-unused exceptions related to former SSH channels (#3681)

See PR #3677 for removal of SSH channel code, and issue #3515 for an
overall channel removal.

## Type of change

- Code maintenance/cleanup

docs/reference.rst

@@ -170,11 +170,6 @@ Exceptions
     parsl.providers.errors.SchedulerMissingArgs
     parsl.providers.errors.ScriptPathError
     parsl.channels.errors.ChannelError
-    parsl.channels.errors.BadHostKeyException
-    parsl.channels.errors.BadScriptPath
-    parsl.channels.errors.BadPermsScriptPath
-    parsl.channels.errors.AuthException
-    parsl.channels.errors.SSHException
     parsl.channels.errors.FileCopyException
     parsl.executors.high_throughput.errors.WorkerLost
     parsl.executors.high_throughput.interchange.ManagerLost

parsl/channels/errors.py

@@ -17,73 +17,6 @@ def __str__(self) -> str:
         return "Hostname:{0}, Reason:{1}".format(self.hostname, self.reason)
 
 
-class BadHostKeyException(ChannelError):
-    ''' SSH channel could not be created since server's host keys could not
-    be verified
-
-    Contains:
-    reason(string)
-    e (paramiko exception object)
-    hostname (string)
-    '''
-
-    def __init__(self, e: Exception, hostname: str) -> None:
-        super().__init__("SSH channel could not be created since server's host keys could not be "
-                         "verified", e, hostname)
-
-
-class BadScriptPath(ChannelError):
-    ''' An error raised during execution of an app.
-    What this exception contains depends entirely on context
-    Contains:
-    reason(string)
-    e (paramiko exception object)
-    hostname (string)
-    '''
-
-    def __init__(self, e: Exception, hostname: str) -> None:
-        super().__init__("Inaccessible remote script dir. Specify script_dir", e, hostname)
-
-
-class BadPermsScriptPath(ChannelError):
-    ''' User does not have permissions to access the script_dir on the remote site
-
-    Contains:
-    reason(string)
-    e (paramiko exception object)
-    hostname (string)
-    '''
-
-    def __init__(self, e: Exception, hostname: str) -> None:
-        super().__init__("User does not have permissions to access the script_dir", e, hostname)
-
-
-class AuthException(ChannelError):
-    ''' An error raised during execution of an app.
-    What this exception contains depends entirely on context
-    Contains:
-    reason(string)
-    e (paramiko exception object)
-    hostname (string)
-    '''
-
-    def __init__(self, e: Exception, hostname: str) -> None:
-        super().__init__("Authentication to remote server failed", e, hostname)
-
-
-class SSHException(ChannelError):
-    ''' if there was any other error connecting or establishing an SSH session
-
-    Contains:
-    reason(string)
-    e (paramiko exception object)
-    hostname (string)
-    '''
-
-    def __init__(self, e: Exception, hostname: str) -> None:
-        super().__init__("Error connecting or establishing an SSH session", e, hostname)
-
-
 class FileCopyException(ChannelError):
     ''' File copy operation failed