Always try GET if HEAD fails when validating URLs.

Fixes problem in CocoaPods/Specs#10341

lib/cocoapods/validator.rb

@@ -236,7 +236,7 @@ module Pod
         loop do
           resp = ::REST.head(url)
 
-          if resp.status_code == 405
+          if resp.status_code >= 400
             resp = ::REST.get(url)
           end
 

spec/unit/validator_spec.rb

@@ -98,6 +98,7 @@ module Pod
 
         it "checks if the homepage is valid" do
           WebMock::API.stub_request(:head, /not-found/).to_return(:status => 404)
+          WebMock::API.stub_request(:get, /not-found/).to_return(:status => 404)
           Specification.any_instance.stubs(:homepage).returns('http://banana-corp.local/not-found/')
           @sut.validate
           @sut.results.map(&:to_s).first.should.match /The URL (.*) is not reachable/
@@ -127,6 +128,14 @@ module Pod
           @sut.results.length.should.equal 0
         end
 
+        it "does not fail if the homepage errors on HEAD" do
+          WebMock::API.stub_request(:head, /page/).to_return( :status => 500 )
+          WebMock::API.stub_request(:get, /page/).to_return( :status => 200 )
+          Specification.any_instance.stubs(:homepage).returns('http://banana-corp.local/page/')
+          @sut.validate
+          @sut.results.length.should.equal 0
+        end
+
         it "does not follow redirects infinitely" do
           WebMock::API.stub_request(:head, /redirect/).to_return(
             :status => 301,