Feature Request: Add option to pod install to fail if any warnings are emitted

[72A12F4E]

When doing a pod install, I often get warnings like the following

Pod installation complete! There are 33 dependencies from the Podfile and 63 total pods installed.

[!] `<PBXResourcesBuildPhase UUID=`2E14AAE21E7C267E00C2D465`>` attempted to initialize an object with an unknown UUID. `1A2F35A41F28EE0100BC1A6D` for attribute: `files`. This can be the result of a merge and  the unknown UUID is being discarded.

[!] `<PBXResourcesBuildPhase UUID=`2E14AAE21E7C267E00C2D465`>` attempted to initialize an object with an unknown UUID. `2F062F561F54828700588292` for attribute: `files`. This can be the result of a merge and  the unknown UUID is being discarded.

This is often the result of a bad merge during development. It would be nice if I could make pod install fail if warnings like this come up, so my dev teams can correct them immediately.

[dnkoutso]

Sure I think its a fairly easy enhancement and starter task for anyone who wants to contribute!

[72A12F4E]

If anyone else wants a quick workaround for their CI purposes, try this

pod install 2>&1 | tee pod-install-output.txt
if (grep -q '\[!\]' pod-install-output.txt); then
    echo "'pod install' finished with warnings! 😢"
    exit 1
fi