Failed to fetch...IP Not Found

Reference: https://unix.stackexchange.com/questions/685521/dnsutils-installation-error-on-raspberry-pi

Sometimes, upgrading or installing ardpkg may result in some errors. These may be related to the Linux repository being moved. When running an apt install command such as apt-get install -y python3-pip , if you get an error like...

E: Failed to fetch http://raspbian.raspberrypi.org/raspbian/pool/main/p/python3.7/libpython3.7-dev_3.7.3-2_armhf.deb  404  Not Found [IP: 93.93.128.193 80]
E: Failed to fetch http://raspbian.raspberrypi.org/raspbian/pool/main/p/python-cryptography/python3-cryptography_2.6.1-3_armhf.deb  404  Not Found [IP: 93.93.128.193 80]
E: Failed to fetch http://raspbian.raspberrypi.org/raspbian/pool/main/p/python3.7/python3.7-dev_3.7.3-2_armhf.deb  404  Not Found [IP: 93.93.128.193 80]
E: Unable to fetch some archives, maybe run apt-get update or try with --fix-missing

Then do the following:

apt-get update --allow-releaseinfo-change
...then try and install the package....eg...
apt-get install -y python3-pip