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##### SUMMARY
If you don't have an ssh client installed in container image or on your system, ansible just throws following error -  `The error was: FileNotFoundError: [Errno 2] No such file or directory: b'ssh': b'ssh'` error. 

```
TASK [Gathering Facts] *********************************************************
[WARNING]: Unhandled error in Python interpreter discovery for host <hostname1>: [Errno 2] No such file or directory: b'ssh': b'ssh'

[WARNING]: Unhandled error in Python interpreter discovery for host <hostname2>: [Errno 2] No such file or directory: b'ssh': b'ssh'

An exception occurred during task execution. To see the full traceback, use -vvv. The error was: FileNotFoundError: [Errno 2] No such file or directory: b'ssh': b'ssh'
fatal: [<hostname1>]: FAILED! => {"msg": "Unexpected failure during module execution.", "stdout": ""}

An exception occurred during task execution. To see the full traceback, use -vvv. The error was: FileNotFoundError: [Errno 2] No such file or directory: b'ssh': b'ssh'
fatal: [<hostname2>]: FAILED! => {"msg": "Unexpected failure during module execution.", "stdout": ""}
```

##### ISSUE TYPE
- Bug Report

##### COMPONENT NAME
<!--- Write the short name of the module, plugin, task or feature below, use your best guess if unsure -->

##### ANSIBLE VERSION
<!--- Paste verbatim output from "ansible --version" between quotes -->
```paste below
2.9.6
```

##### STEPS TO REPRODUCE
<!--- Describe exactly how to reproduce the problem, using a minimal test-case -->
Run playbook on the system where ssh client is not installed & playbook is expecting to use ssh keys for remote hosts.


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##### EXPECTED RESULTS
<!--- Describe what you expected to happen when running the steps above -->
If possible adding an error message indicating `ssh client is not installed on the system`

##### ACTUAL RESULTS
<!--- Describe what actually happened. If possible run with extra verbosity (-vvvv) -->

<!--- Paste verbatim command output between quotes -->
```paste below
Error message mentioned in the summary 
The error was: FileNotFoundError: [Errno 2] No such file or directory: b'ssh': b'ssh'
```

Thank you!!
'''
        Takes a command array and scans it for ControlPersist and ControlPath
        settings and returns two booleans indicating whether either was found.
        This could be smarter, e.g. returning false if ControlPersist is 'no',
        but for now we do it simple way.
        '''
        controlpersist = False
        controlpath = False
        for b_arg in (a.lower() for a in b_command):
            if b'controlpersist' in b_arg:
                controlpersist = True
            elif b'controlpath' in b_arg:
                controlpath = True
        return controlpersist, controlpath
    def _add_args(self, b_command, b_args, explanation):
        """
        Adds arguments to the ssh command and displays a caller-supplied explanation of why.
        :arg b_command: A list containing the command to add the new arguments to.
            This list will be modified by this method.
        :arg b_args: An iterable of new arguments to add.  This iterable is used
            more than once so it must be persistent (ie: a list is okay but a
            StringIO would not)
        :arg explanation: A text string containing explaining why the arguments
            were added.  It will be displayed with a high enough verbosity.
        .. note:: This function does its work via side-effect.  The b_command list has the new arguments appended.
        """
        display.vvvvv(u'SSH: %s: (%s)' % (explanation, ')('.join(to_text(a) for a in b_args)), host=self._play_context.remote_addr)
        b_command += b_args
    def _build_command(self, binary, *other_args):