# Buggy code
def _post_connect(self):
    """! @brief Finish the connect process.

    The session is opened. The `no_init` parameter passed to the constructor determines whether the
    board and target are initialized.

    If an ELF file was provided on the command line, it is set on the target.

    @param self This object.
    @param session A @ref pyocd.core.session.Session "Session" instance.
    @retval True Session attached and context state inited successfully.
    @retval False An error occurred when opening the session or initing the context state.
    """
    assert self.session is not None
    assert not self.session.is_open

    # Open the session.
    try:
        self.session.open(init_board=not self.args.no_init)
    except exceptions.TransferFaultError as e:
        if not self.session.target.is_locked():
            self.context.writei("Transfer fault while initing board: %s", e)
            if self.session.log_tracebacks:
                self.context.write(traceback.format_exc())
            return False
    except exceptions.Error as e:
        self.context.writei("Exception while initing board: %s", e)
        if self.session.log_tracebacks:
            self.context.write(traceback.format_exc())
        return False

    # Set elf file if provided.
    if self.args.elf:
        self.target.elf = os.path.expanduser(self.args.elf)

    # Handle a device with flash security enabled.
    if not self.args.no_init and self.session.target.is_locked():
        self.context.write(
            "Warning: Target is locked, limited operations available. Use 'unlock' "
            "command to mass erase and unlock, then execute 'reinit'."
        )

    return True


# Traceback (NameError)
$ pyocd commander --target=stm32g031j6mx --elf DISCO.elf
0001015:CRITICAL:__main__:uncaught exception: name 'os' is not defined
Traceback (most recent call last):
File "/home/saa/.local/lib/python3.7/site-packages/pyocd-0.28.1.dev6-py3.7.egg/pyocd/__main__.py", line 398, in run
self._COMMANDS[self._args.cmd](self)
File "/home/saa/.local/lib/python3.7/site-packages/pyocd-0.28.1.dev6-py3.7.egg/pyocd/__main__.py", line 802, in do_commander
PyOCDCommander(self._args, cmds).run()
File "/home/saa/.local/lib/python3.7/site-packages/pyocd-0.28.1.dev6-py3.7.egg/pyocd/commands/commander.py", line 63, in run
if not self.connect():
File "/home/saa/.local/lib/python3.7/site-packages/pyocd-0.28.1.dev6-py3.7.egg/pyocd/commands/commander.py", line 178, in connect
self._post_connect()
File "/home/saa/.local/lib/python3.7/site-packages/pyocd-0.28.1.dev6-py3.7.egg/pyocd/commands/commander.py", line 218, in _post_connect
self.target.elf = os.path.expanduser(self.args.elf)
NameError: name 'os' is not defined

# Fixed code
def _post_connect(self):
    """! @brief Finish the connect process.

    The session is opened. The `no_init` parameter passed to the constructor determines whether the
    board and target are initialized.

    If an ELF file was provided on the command line, it is set on the target.

    @param self This object.
    @param session A @ref pyocd.core.session.Session "Session" instance.
    @retval True Session attached and context state inited successfully.
    @retval False An error occurred when opening the session or initing the context state.
    """
    assert self.session is not None
    assert not self.session.is_open

    # Open the session.
    try:
        self.session.open(init_board=not self.args.no_init)
    except exceptions.TransferFaultError as e:
        if not self.session.target.is_locked():
            self.context.writei("Transfer fault while initing board: %s", e)
            if self.session.log_tracebacks:
                self.context.write(traceback.format_exc())
            return False
    except exceptions.Error as e:
        self.context.writei("Exception while initing board: %s", e)
        if self.session.log_tracebacks:
            self.context.write(traceback.format_exc())
        return False

    # Set elf file if provided.
    if self.args.elf:
        self.session.target.elf = os.path.expanduser(self.args.elf)

    # Handle a device with flash security enabled.
    if not self.args.no_init and self.session.target.is_locked():
        self.context.write(
            "Warning: Target is locked, limited operations available. Use 'unlock' "
            "command to mass erase and unlock, then execute 'reinit'."
        )

    return True