[Fix rubocop/rubocop-ast#7] Reimport error from rubocop-ast

lib/rubocop.rb

@@ -18,6 +18,7 @@
 require_relative 'rubocop/platform'
 require_relative 'rubocop/name_similarity'
 require_relative 'rubocop/string_interpreter'
+require_relative 'rubocop/error' unless RuboCop.const_defined?(:Error)
 require_relative 'rubocop/warning'
 
 require_relative 'rubocop/cop/util'

lib/rubocop/error.rb

@@ -0,0 +1,34 @@
+# frozen_string_literal: true
+
+module RuboCop
+  # An Error exception is different from an Offense with severity 'error'
+  # When this exception is raised, it means that RuboCop is unable to perform
+  # a requested action (probably due to misconfiguration) and must stop
+  # immediately, rather than carrying on
+  class Error < StandardError; end
+
+  class ValidationError < Error; end
+
+  # A wrapper to display errored location of analyzed file.
+  class ErrorWithAnalyzedFileLocation < Error
+    def initialize(cause:, node:, cop:)
+      @cause = cause
+      @cop = cop
+      @location = node.is_a?(RuboCop::AST::Node) ? node.loc : node
+    end
+
+    attr_reader :cause, :cop
+
+    def line
+      @location&.line
+    end
+
+    def column
+      @location&.column
+    end
+
+    def message
+      "cause: #{cause.inspect}"
+    end
+  end
+end

lib/rubocop/runner.rb

@@ -361,7 +361,11 @@ def get_processed_source(file)
       if @options[:stdin]
         ProcessedSource.new(@options[:stdin], ruby_version, file)
       else
-        ProcessedSource.from_file(file, ruby_version)
+        begin
+          ProcessedSource.from_file(file, ruby_version)
+        rescue Errno::ENOENT
+          raise RuboCop::Error, "No such file or directory: #{file}"
+        end
       end
     end