Error Watlow

$ sudo watlow /dev/ttyUSB0
Traceback (most recent call last):
  File "/home/pi/Repositories/watlow/watlow/__init__.py", line 44, in command_line
    state = temperature_controller.get()
  File "/home/pi/Repositories/watlow/watlow/driver.py", line 100, in get
    check=self.responses[key]
  File "/home/pi/Repositories/watlow/watlow/driver.py", line 147, in _write_and_read
    return self._write_and_read(request, length, check, retries-1)
  File "/home/pi/Repositories/watlow/watlow/driver.py", line 147, in _write_and_read
    return self._write_and_read(request, length, check, retries-1)
  File "/home/pi/Repositories/watlow/watlow/driver.py", line 147, in _write_and_read
    return self._write_and_read(request, length, check, retries-1)
  File "/home/pi/Repositories/watlow/watlow/driver.py", line 133, in _write_and_read
    raise IOError("Could not communicate with Watlow.")
OSError: Could not communicate with Watlow.

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/local/bin/watlow", line 33, in <module>
    sys.exit(load_entry_point('watlow', 'console_scripts', 'watlow')())
  File "/home/pi/Repositories/watlow/watlow/__init__.py", line 47, in command_line
    temperature_controller.close()
  File "/home/pi/Repositories/watlow/watlow/driver.py", line 90, in close
    self.connection.flush()
  File "/usr/local/lib/python3.7/dist-packages/serial/serialposix.py", line 672, in flush
    raise PortNotOpenError()
serial.serialutil.PortNotOpenError: Attempting to use a port that is not open

New Error

Traceback (most recent call last):
  File "/usr/local/bin/watlow", line 33, in <module>
    sys.exit(load_entry_point('watlow', 'console_scripts', 'watlow')())
  File "/home/pi/Repositories/watlow/watlow/__init__.py", line 40, in command_line
    temperature_controller = TemperatureController(port=args.port)
  File "/home/pi/Repositories/watlow/watlow/driver.py", line 78, in __init__
    self.open()
  File "/home/pi/Repositories/watlow/watlow/driver.py", line 82, in open
    self.connection = serial.Serial(
AttributeError: module 'serial' has no attribute 'Serial'


Python Script to run...
from time import sleep
import serial
connection = serial.Serial('/dev/ttyUSB0', 38400)
try:
    connection.write('55FF0510000006E8010301040101E399'.decode('hex'))
    sleep(1)
    print(connection.read(connection.inWaiting()).encode('hex'))
finally:
    connection.close()