I installed FixCode 0.3.0 in Xcode 7.3 (7D175) via fastlane install_xcode_plugin and also tried via Alcatraz (remove, install again) but I'm still getting this:

I would assume that this is the kind of stuff FixCode should take care of.
Maybe also helpful: When I started Xcode after installing Alcatraz I was asked if I want to enable that plugin but I was never asked for FixCode.
But I can confirm the existance of /Users/myuser/Library/Application\ Support/Developer/Shared/Xcode/Plug-ins/FixCode.xcplugin
It also has the same permissions as Alcatraz.xcplugin.
I installed FixCode 0.3.0 in Xcode 7.3 (7D175) via fastlane install_xcode_plugin and also tried via Alcatraz (remove, install again) but I'm still getting this:

I would assume that this is the kind of stuff FixCode should take care of.
Maybe also helpful: When I started Xcode after installing Alcatraz I was asked if I want to enable that plugin but I was never asked for FixCode.
But I can confirm the existance of /Users/myuser/Library/Application\ Support/Developer/Shared/Xcode/Plug-ins/FixCode.xcplugin
It also has the same permissions as Alcatraz.xcplugin.