I wanted to move a file to a /usr/python2.7/ but i was unable to do so, so i changed the permissions of /usr to myuser:

sudo chown -R ***** /usr

it worked but i realised it was a blunder when sudo stopped working after that. It says:

sudo: effective uid is not 0, is sudo installed setuid root?

I have seen this post where the accepted solution was to use the policykit:

pkexec chown root:root /usr/bin/sudo
pkexec chmod 4755 /usr/bin/sudo

however, even the policykit is saying that:

pkexec must be setuid root

please help, i've learned a lesson and will never change permissions for /usr again. Please help me this time!