Revert "[Analyzer] Allow using CocoaPods with only externally-sourced…

Revert "[Analyzer] Allow using CocoaPods with only externally-sourced dependencies in a   `Podfile` without specifying a source or displaying a warning"

This reverts commit 2cc9f01d.

Follow-up to https://github.com/CocoaPods/CocoaPods/commit/7840787e05afb1da24bcfafa4a62f0de41ebf07a.

Conflicts:
	lib/cocoapods/installer/analyzer.rb

CHANGELOG.md

@@ -96,11 +96,6 @@ To install or update CocoaPods see this [guide](http://docs.cocoapods.org/guides
   [Kyle Fuller](https://github.com/kylef)
   [#1249](https://github.com/CocoaPods/CocoaPods/issues/1249)
 
-* Allows using CocoaPods with only externally-sourced dependencies in a
-  `Podfile` without specifying a source or displaying a warning.  
-  [Samuel Giddins](https://github.com/segiddins)
-  [#2735](https://github.com/CocoaPods/CocoaPods/issues/2735)
-
 
 ## 0.34.4
 

lib/cocoapods/installer/analyzer.rb

@@ -379,7 +379,7 @@ module Pod
       def sources
         @sources ||= begin
           sources = podfile.sources
-          if sources.empty? && !podfile.dependencies.reject(&:external_source).empty?
+          if sources.empty?
             SourcesManager.all
           else
             sources.map do |url|

spec/unit/installer/analyzer_spec.rb

@@ -595,13 +595,6 @@ module Pod
             UI.warnings.should.
               match %r{source 'https://github.com/CocoaPods/Specs.git'}
           end
-
-          it 'does not warn when all dependencies have an external source' do
-            UI.warnings = ''
-            @podfile.stubs(:dependencies).returns([Dependency.new('SEGModules', :git => 'https://github.com/segiddins/SEGModules.git')])
-            @analyzer.send(:sources)
-            UI.warnings.should.be.empty?
-          end
         end
 
         describe 'when there are explicit sources' do