Not a question... a report of "how to", I hope. Maybe spare the next person. Inspire the programmers.
HOURS spent by me, new to Pi, old to computers today.
Wonderful experiences initially... then tried to connect my Pi 3 B, ver 1.2 to my Wi-Fi.
(Yes, did sudo apt update, upgrade... about 1pm New York time, 5 Aug 2018)
And unplugged wired connection and rebooted BEFORE trying, again, to connect to my Wi-Fi.
I'm pretty sure the Wi-Fi is using WEP security. (Yes, stone age... I know. I have some old devices that won't connect otherwise.)
I used the ordinary GUI "connect to Wi-Fi", and after filling in the "Pre-shared key" box, clicked "OK", dialog went away (no messages), and my screen just looked at me. Red X's on the icon for the network connection.
Tried lots and lots and lots of things.
Here's what worked...
1) used sudo nano /etc/wpa_supplicant/wpa_supplicant.conf to take the system-created double quotes OFF of the characters following wep_key0=
2) (save the new .conf file, on top of old one)
4) Just wait... less than 15 seconds. Hurrah! Network icon becomes a signal strength indicator!
DANGER- try to change the Wi-Fi you are connected to? The system will put the double quotes back, and you have to do it all over again. Sigh. (I wonder if just deleting the wep_key0= line would be as easy... but after the HOURS to get this far, and write up, I haven't the energy to try it! Or, perhaps some value other than "NONE" on the key_mgmt line... but putting WEP made things WORSE... from memory: Made system say "no Wi-Fi i/f found"!)
LEAVE the double quotes around the SSID spec.
Sigh. Aren't computers fun? At least I had the encouraging positive experience before hitting the near brick wall!