Comment 1 for bug 1575652

I am facing the similar issue while attempting to PXE boot Ubuntu 16.04 LTS version over corporate Network
This looks like a 100% bug because I followed the exact same steps as Ubuntu 14.x and 15.x however earlier versions PXE install
smoothly whereas Ubuntu 16.04 LTS version errors out saying "installation error ocurred" and logs show live installer image not found , Can't open /usr/lib/fetch-url//cdromhttp

As you can see its prefixing cdrom which should not happen. I have spent hours testing and finding workarounds for this however this seems like a bug in the code. Request you to fix this. We are currently doing a POC on 16.04 LTS and if everything goes successfully, we may need to mass deploy this in our environment. We can't be deploying using CDROM on every machine and need to a mechanism where PXE via netboot works smoothly

Request the developers to have a look at this and come up with a patch or fix for this.