[rubygems/rubygems] Reject unknown platforms when running bundle lock --add-platform

https://github.com/rubygems/rubygems/commit/1f93a2bdc5

lib/bundler/cli/lock.rb

@@ -48,8 +48,8 @@ module Bundler
         options["add-platform"].each do |platform_string|
           platform = Gem::Platform.new(platform_string)
           if platform.to_s == "unknown"
-            Bundler.ui.warn "The platform `#{platform_string}` is unknown to RubyGems " \
-              "and adding it will likely lead to resolution errors"
+            Bundler.ui.error "The platform `#{platform_string}` is unknown to RubyGems and can't be added to the lockfile."
+            exit 1
           end
           definition.add_platform(platform)
         end

spec/bundler/commands/lock_spec.rb

@@ -857,9 +857,10 @@ RSpec.describe "bundle lock" do
     expect(lockfile.platforms).to match_array(default_platform_list("ruby"))
   end
 
-  it "warns when adding an unknown platform" do
-    bundle "lock --add-platform foobarbaz"
-    expect(err).to include("The platform `foobarbaz` is unknown to RubyGems and adding it will likely lead to resolution errors")
+  it "fails when adding an unknown platform" do
+    bundle "lock --add-platform foobarbaz", raise_on_error: false
+    expect(err).to include("The platform `foobarbaz` is unknown to RubyGems and can't be added to the lockfile")
+    expect(last_command).to be_failure
   end
 
   it "allows removing platforms" do