Fix “Unable to locate package” error in Kali Linux.

This error is basically due to entries in the sources.list file.
Open /etc/apt/ using following command:
cd /etc/apt/
Open the sources.list file using:
sudo nano sources.list
Now paste the following code at the last line of the file:
deb http://http.kali.org/kali kali-rolling main contrib non-free
# For source package access, uncomment the following line
# deb-src http://http.kali.org/kali kali-rolling main contrib non-free
deb http://http.kali.org/kali sana main non-free contrib
deb http://security.kali.org/kali-security sana/updates main contrib non-free
# For source package access, uncomment the following line
# deb-src http://http.kali.org/kali sana main non-free contrib
# deb-src http://security.kali.org/kali-security sana/updates main contrib non-free
deb http://old.kali.org/kali moto main non-free contrib
# For source package access, uncomment the following line
# deb-src http://old.kali.org/kali moto main non-free contrib
Write and quit the file using CTRL+O and CTRL+X

Now just run:
sudo apt-get update
Now your error is gone you can install any package