Open your terminal and type following commands – (Replace PUBLIC_KEY_ID with the error id displayed)
gpg –keyserver keyserver.ubuntu.com –recv PUBLIC_KEY_ID
gpg –export –armor PUBLIC_KEY_ID | sudo apt-key add –
I'll write mostly about brain eaters( common issues faced by developers :P ) and some tips
Open your terminal and type following commands – (Replace PUBLIC_KEY_ID with the error id displayed)
gpg –keyserver keyserver.ubuntu.com –recv PUBLIC_KEY_ID
gpg –export –armor PUBLIC_KEY_ID | sudo apt-key add –