No module named 'arrow'

[Hisfantor]

Used: Ubuntu 18.04 Python 3

I used sudo apt-get install python3-pyqt4 to install pyqt4
then I run: python3 RESTool_main.py
and got:

Traceback (most recent call last):
  File "RESTool_main.py", line 32, in <module>
    import arrow
ModuleNotFoundError: No module named 'arrow'

Note: pip install PyQt4 didn't seem to work and gave me:

Could not find a version that satisfies the requirement PyQt4 (from versions: )
No matching distribution found for PyQt4