Test suite: drop workarounds for running on Stretch

features/scripts/opencv_match_template.py

 #!/usr/bin/env python3
 
-# XXX:Buster: when we drop support for Stretch we can remove this
-# import.
-from __future__ import print_function
-
 import cv2
 import os
 import sys

features/step_definitions/erase_memory.rb

@@ -226,10 +226,8 @@ When /^I fill a (\d+) MiB file with a known pattern on the (persistent|root) fil
   end
   # Note that `yes` prints its own newline, so we have to skip it in
   # `pattern` below.
-  # XXX:Stretch: once we drop support < Buster we can improve the
-  # expression below to `pattern[..-2]`.
   $vm.execute_successfully(
-    "yes #{pattern[0, pattern.length - 1]} | " \
+    "yes #{pattern[0..-2]} | " \
     "dd of=#{dest_file} bs=#{pattern.size} count=#{pattern_nb}"
   )
 end

features/step_definitions/mac_spoofing.rb

@@ -104,14 +104,7 @@ end
 
 When /^I hotplug a network device( and wait for it to be initialized)?$/ do |wait|
   initial_nr_nics = wait ? all_ethernet_nics.size : nil
-  # XXX:Buster: when we stop supporting the test suite on Stretch
-  # hosts, let's remove this workaround related to #14819 and just
-  # settle on a device that works on all supported platforms.
-  device = if cmd_helper('lsb_release --short --codename').chomp == 'stretch'
-             'virtio'
-           else
-             'pcnet'
-           end
+  device = 'pcnet'
   debug_log("Hotplugging a '#{device}' network device")
   xml = <<-XML
     <interface type='network'>

features/step_definitions/pidgin.rb

@@ -113,9 +113,7 @@ Given /^my XMPP friend goes online( and joins the multi-user chat)?$/ do |join_c
     account['username'] + '@' + account['domain'],
     account['password'],
     account['otr_key'],
-    # XXX:Buster: once we stop supporting running our test suite on Stretch,
-    # replace this with: **(bot_opts.transform_keys(&:to_sym))
-    **(bot_opts.each_with_object({}) { |(k, v), a| a[k.to_sym] = v })
+    **(bot_opts.transform_keys(&:to_sym))
   )
   @chatbot.start
   add_after_scenario_hook { @chatbot.stop }

features/step_definitions/totem.rb

@@ -5,7 +5,7 @@ Given /^I create sample videos$/ do
   @video_dir_on_host = "#{$config['TMPDIR']}/video_dir"
   FileUtils.mkdir_p(@video_dir_on_host)
   add_after_scenario_hook { FileUtils.rm_r(@video_dir_on_host) }
-  fatal_system("#{ffmpeg} -loop 1 -t 30 -f image2 " \
+  fatal_system('ffmpeg -loop 1 -t 30 -f image2 ' \
                "-i 'features/images/USBTailsLogo.png' " \
                '-an -vcodec libx264 -y ' \
                '-filter:v "crop=in_w-mod(in_w\,2):in_h-mod(in_h\,2)" ' \

features/support/helpers/dogtail.rb

@@ -117,8 +117,7 @@ module Dogtail
         'False'
       elsif value.class == String
         "'#{value}'"
-      # XXX:Buster: drop the Fixnum line once we stop supporting Stretch
-      elsif [Fixnum, Integer, Float].include?(value.class) # rubocop:disable Lint/UnifiedInteger
+      elsif [Integer, Float].include?(value.class)
         v.to_s
       else
         raise "#{self.class.name} does not know how to handle argument type " \

features/support/helpers/misc_helpers.rb

@@ -35,14 +35,7 @@ end
 
 def time_delta(start_time, now)
   elapsed = now - start_time
-  # XXX: Drop this version check when we drop support for running the test suite
-  # on Debian Stretch.
-  if Gem::Version.new(RUBY_VERSION) < Gem::Version.new('2.4')
-    format('%<elapsed>.2f', elapsed: elapsed)
-      .chomp('.00').chomp('.0').chomp('0')
-  else
-    elapsed.ceil(2)
-  end
+  elapsed.ceil(2)
 end
 
 # Call block (ignoring any exceptions it may throw) repeatedly with
@@ -394,8 +387,6 @@ def dbus_send_get_shellcommand(service, object_path, method, *args, **opts)
   opts ||= {}
   ruby_type_to_dbus_type = {
     String  => 'string',
-    # XXX:Buster: drop the Fixnum line once we stop supporting Stretch
-    Fixnum  => 'int32', # rubocop:disable Lint/UnifiedInteger
     Integer => 'int32',
   }
   typed_args = args.map do |arg|
@@ -426,14 +417,6 @@ def dbus_send(*args, **opts)
   dbus_send_ret_conv(ret)
 end
 
-def ffmpeg
-  if cmd_helper('lsb_release --short --codename').chomp == 'stretch'
-    'avconv'
-  else
-    'ffmpeg'
-  end
-end
-
 # This is IO.popen() that ensures that we wait() for the subprocess to
 # finish. Please use this instead IO.popen() when running a subprocess
 # inside a try_for() or other Timeout::timeout() block!

features/support/helpers/opencv.rb

@@ -4,12 +4,6 @@ class OpenCVInternalError < StandardError
 end
 
 module OpenCV
-  @python = if cmd_helper('lsb_release --short --codename').chomp == 'stretch'
-              'python2.7'
-            else
-              'python3'
-            end
-
   def self.matchTemplate(image, screen, sensitivity, show_match)
     assert(sensitivity < 1.0)
     # Do a deep-copy so we don't mess up the outer environment
@@ -20,7 +14,7 @@ module OpenCV
       env['DISPLAY'] = ENV['USER_DISPLAY']
     end
     p = popen_wait(
-      [env, @python, "#{GIT_DIR}/features/scripts/opencv_match_template.py",
+      [env, 'python3', "#{GIT_DIR}/features/scripts/opencv_match_template.py",
        screen, image, sensitivity.to_s, show_match.to_s,],
       err: [:child, :out]
     )

features/support/hooks.rb

@@ -224,7 +224,7 @@ Before('@product') do |scenario|
   if $config['CAPTURE']
     video_name = sanitize_filename("#{scenario.name}.mkv")
     @video_path = "#{ARTIFACTS_DIR}/#{video_name}"
-    capture = IO.popen([ffmpeg,
+    capture = IO.popen(['ffmpeg',
                         '-f', 'x11grab',
                         '-s', '1024x768',
                         '-r', '15',