diff --git a/.rubocop.yml b/.rubocop.yml
index 9a14d206e..84d6a7c5b 100644
--- a/.rubocop.yml
+++ b/.rubocop.yml
@@ -4,6 +4,7 @@ AllCops:
   Exclude:
     - doc/**/*.rb
     - rake.gemspec
+    - bin/*
 
 Metrics/LineLength:
   Enabled: true
diff --git a/.travis.yml b/.travis.yml
index 9e7100420..b0bf3ebe3 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,5 +1,4 @@
 language: ruby
-sudo: false
 rvm:
   - 2.0.0
   - 2.1.10
@@ -7,6 +6,7 @@ rvm:
   - 2.3.8
   - 2.4.5
   - 2.5.3
+  - 2.6.1
   - ruby-head
   - jruby-9.2.4.0
   - jruby-head
@@ -19,4 +19,6 @@ matrix:
 before_script:
   - unset JRUBY_OPTS
   - unset _JAVA_OPTIONS
+  - if ruby -e "exit RUBY_VERSION >= '2.3.0'"; then gem update --system=3.0.1; else gem update --system=2.7.8; fi
+
 script: ruby -Ilib exe/rake
diff --git a/History.rdoc b/History.rdoc
index 455b27dd9..16b6331a1 100644
--- a/History.rdoc
+++ b/History.rdoc
@@ -1,3 +1,14 @@
+=== 12.3.3
+
+==== Bug fixes
+
+* Use the application's name in error message if a task is not found.
+  Pull Request #303 by tmatilai
+
+==== Enhancements:
+
+* Use File.open explicitly.
+
 === 12.3.2
 
 ==== Bug fixes
diff --git a/azure-pipelines.yml b/azure-pipelines.yml
new file mode 100644
index 000000000..19cce3eeb
--- /dev/null
+++ b/azure-pipelines.yml
@@ -0,0 +1,11 @@
+jobs:
+- job: macOS
+  pool:
+    vmImage: 'macos-10.13'
+  steps:
+  - script: |
+      gem install bundler
+      bundle install --retry=3 --jobs=4
+    displayName: 'bundle install'
+  - script: ruby -Ilib exe/rake
+    displayName: 'ruby -Ilib exe/rake'
diff --git a/lib/rake/file_list.rb b/lib/rake/file_list.rb
index 15ea4b36d..22c339f24 100644
--- a/lib/rake/file_list.rb
+++ b/lib/rake/file_list.rb
@@ -294,7 +294,7 @@ def egrep(pattern, *options)
       matched = 0
       each do |fn|
         begin
-          open(fn, "r", *options) do |inf|
+          File.open(fn, "r", *options) do |inf|
             count = 0
             inf.each do |line|
               count += 1
diff --git a/lib/rake/task_manager.rb b/lib/rake/task_manager.rb
index d503a3044..1991088fa 100644
--- a/lib/rake/task_manager.rb
+++ b/lib/rake/task_manager.rb
@@ -60,7 +60,8 @@ def [](task_name, scopes=nil)
     end
 
     def generate_message_for_undefined_task(task_name)
-      message = "Don't know how to build task '#{task_name}' (See the list of available tasks with `rake --tasks`)"
+      message = "Don't know how to build task '#{task_name}' "\
+                "(See the list of available tasks with `#{Rake.application.name} --tasks`)"
       message + generate_did_you_mean_suggestions(task_name)
     end
 
diff --git a/lib/rake/version.rb b/lib/rake/version.rb
index 53ba15e0e..6014e9322 100644
--- a/lib/rake/version.rb
+++ b/lib/rake/version.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 module Rake
-  VERSION = "12.3.2"
+  VERSION = "12.3.3"
 
   module Version # :nodoc: all
     MAJOR, MINOR, BUILD, *OTHER = Rake::VERSION.split "."
diff --git a/rake.gemspec b/rake.gemspec
index ddc9f2a61..66c567ca9 100644
--- a/rake.gemspec
+++ b/rake.gemspec
@@ -24,7 +24,7 @@ Rake has the following features:
   s.licenses = ["MIT".freeze]
 
   s.files = %x[git ls-files -z].split("\x0").reject { |f| f.match(%r{^(test|spec|features)/}) } -
-            %w[.rubocop.yml .travis.yml appveyor.yml]
+            %w[.rubocop.yml .gitignore .travis.yml appveyor.yml]
   s.bindir = "exe"
   s.executables = s.files.grep(%r{^exe/}) { |f| File.basename(f) }
   s.require_paths = ["lib".freeze]
diff --git a/test/helper.rb b/test/helper.rb
index 7d0989a38..64f7db7e2 100644
--- a/test/helper.rb
+++ b/test/helper.rb
@@ -2,7 +2,7 @@
 $:.unshift File.expand_path("../../lib", __FILE__)
 
 begin
-  if ENV['COVERALLS']
+  if ENV["COVERALLS"]
     gem "coveralls"
     require "coveralls"
     Coveralls.wear!
@@ -28,7 +28,7 @@ class TaskManager
     include Rake::TaskManager
   end
 
-  RUBY = ENV["BUNDLE_RUBY"] || Gem.ruby
+  RUBY = File.realpath(ENV["BUNDLE_RUBY"] || Gem.ruby)
 
   def setup
     ARGV.clear
diff --git a/test/test_rake_task.rb b/test/test_rake_task.rb
index ee3e9d35c..688e0a3e7 100644
--- a/test/test_rake_task.rb
+++ b/test/test_rake_task.rb
@@ -172,7 +172,8 @@ def test_find
     task :tfind
     assert_equal "tfind", Task[:tfind].name
     ex = assert_raises(RuntimeError) { Task[:leaves] }
-    assert_equal "Don't know how to build task 'leaves' (See the list of available tasks with `rake --tasks`)", ex.message
+    assert_equal "Don't know how to build task 'leaves'" \
+      " (See the list of available tasks with `rake --tasks`)", ex.message
   end
 
   def test_defined
diff --git a/test/test_rake_task_manager.rb b/test/test_rake_task_manager.rb
index 7d8c40902..88937c604 100644
--- a/test/test_rake_task_manager.rb
+++ b/test/test_rake_task_manager.rb
@@ -28,6 +28,16 @@ def test_index
     assert_equal "Don't know how to build task 'bad' (See the list of available tasks with `rake --tasks`)", e.message
   end
 
+  def test_undefined_task_with_custom_application
+    Rake.application.init("myrake", nil)
+
+    e = assert_raises RuntimeError do
+      @tm["bad"]
+    end
+
+    assert_equal "Don't know how to build task 'bad' (See the list of available tasks with `myrake --tasks`)", e.message
+  end
+
   def test_name_lookup
     t = @tm.define_task(Rake::Task, :t)
     assert_equal t, @tm[:t]