Kubuntu 16.04
Note: The following is my adaptation of @ccamara's answer, which didn't quite work as written on my system. If you upvote this answer, you should upvote theirs as well.
Introduction
KWallet needs a password to decrypt its stored passwords, which includes your WiFi password. To avoid having to type a password each time, you can store your WiFi password in an unencrypted file. This allows KWallet to use the WiFi password without dycrypting it.
Warning
If you do this, know that this opens a possible security hole, as any user on your computer could access this file and learn your wifi password.
- Do not use this approach if you need the wifi password to be hidden from other users on this computer.
- If you use your wifi password for other accounts (not recommended!), you may want to hide it so that others would not learn your password and be able to access your other accounts with it.
Of course, it would only be vulnerable to somebody who could access your computer. You probably don't need to worried about your neighbors stealing your wifi password through this approach because they probably will not have access to your computer.
Steps
Right-click on the WiFi icon and click "Configure Network Connections...".
A "Connection editor" window show a list of saved connections. Right-click on the WiFi network you want to work with, and click "Edit..." from the drop-down menu.
This opens a new window, with a "Wi-Fi Security" tab. Click on that tab.
There should be a drop-down menu of security options and a password field. The password field should have an eyeball icon and a disk icon both on the right. Click the disk icon to save the password.
Choose "Store password and make it available for all users (not encrypted)".
Done!