make pdk fails with :: ModuleNotFoundError: No module named 'yaml'

[vijayank88]

Describe the bug
When we install openlane with "git clone https://github.com/The-OpenROAD-Project/OpenLane.git" and following step #make pdk command fail with below error:
Traceback (most recent call last):
File "./dependencies/tool.py", line 15, in
import yaml <---
ModuleNotFoundError: No module named 'yaml'
git clone /home/indir/OpenLane/pdks/skywater-pdk
fatal: repository '/home/indir/OpenLane/pdks/skywater-pdk' does not exist
make: *** [Makefile:87: /home/indir/OpenLane/pdks/skywater-pdk] Error 128

Desktop (please complete the following information):
Important Note::This issue arise only when using below OS.

• OS:Ubuntu 20.04 and Centos 7 and above

Workaround is install pyymal with below command and then try #make pdk
#sudo pip3 install pyyaml
#make pdk

I have tested at end above solution working fine.
@donn Please verify is this valid and approve it, then I will Close this GitHub issue.
Thanks..

[donn]

This isn't a workaround. This is in the Readme.