implemented Xcode license check for all Commands

CHANGELOG.md

@@ -134,6 +134,10 @@ To install release candidates run `[sudo] gem install cocoapods --pre`
 
 ##### Enhancements
 
+* Check for Xcode License Agreement before running commands.
+  [Xavi Matos](https://github.com/CalQL8ed-K-OS)
+  [#3002](https://github.com/CocoaPods/CocoaPods/issues/3002)
+
 * Do not generate targets for Pods without sources.  
   [Boris Bügling](https://github.com/neonichu)
   [#2918](https://github.com/CocoaPods/CocoaPods/issues/2918)

lib/cocoapods/command.rb

@@ -41,6 +41,7 @@ module Pod
 
     def self.run(argv)
       help! 'You cannot run CocoaPods as root.' if Process.uid == 0
+      verify_xcode_license_approved!
 
       super(argv)
       UI.print_warnings
@@ -121,5 +122,24 @@ module Pod
         raise Informative, "No `Podfile.lock' found in the project directory, run `pod install'."
       end
     end
+
+    def self.verify_xcode_license_approved!
+      unless xcode_license_approved?
+        raise Informative, xcode_license_message
+      end
+    end
+
+    def self.xcode_license_approved?
+      !(`/usr/bin/xcrun clang 2>&1` =~ /license/ && !$?.success?)
+    end
+
+    def self.xcode_license_message
+      <<-EOS.strip_heredoc
+          You have not agreed to the Xcode license.
+          The setup command requires you do so.
+          Agree to the license by running:
+          `xcodebuild -license`
+      EOS
+    end
   end
 end