Interate over all lambda functions

Not just the functions returned by the first call to `#list_functions`.

lib/dpl/provider/lambda.rb

@@ -27,9 +27,7 @@ def push_app
 
         function_name = options[:name] || option(:function_name)
 
-        response = lambda.list_functions
-
-        if response.functions.any? { |function| function.function_name == function_name }
+        if all_lambda_functions.any? { |function| function.function_name == function_name }
 
           log "Function #{function_name} already exists, updating."
 
@@ -180,6 +178,19 @@ def cleanup
 
       def uncleanup
       end
+
+      def all_lambda_functions
+        response = lambda.list_functions
+        functions = response.functions
+        marker = response.next_marker
+        until marker.empty? do
+          response = lambda.list_functions(marker: marker)
+          functions += response.functions
+          marker = response.next_marker
+        end
+
+        functions
+      end
     end
   end
 end

spec/provider/lambda_spec.rb

@@ -67,13 +67,15 @@
     }
 
     list_functions_response = {
+      next_marker: "", # no more functions
       functions: [
         { function_name: 'test-function' }
       ]
     }
 
     empty_list_functions_response = {
-        functions: [ ]
+      next_marker: "",
+      functions: [ ]
     }
 
     example_response = {