Simplify return value logic.

Library/Homebrew/cmd/style.rb

@@ -62,6 +62,6 @@ module Homebrew
                                  NewFormulaAudit]
     end
 
-    Homebrew.failed = Style.check_style_and_print(target, options)
+    Homebrew.failed = !Style.check_style_and_print(target, options)
   end
 end

Library/Homebrew/style.rb

@@ -102,7 +102,7 @@ module Homebrew
         raise "Invalid output_type for check_style_impl: #{output_type}"
       end
 
-      return !rubocop_success if files.present? || !has_non_formula
+      return rubocop_success if files.present? || !has_non_formula
 
       shellcheck   = which("shellcheck")
       shellcheck ||= which("shellcheck", ENV["HOMEBREW_PATH"])
@@ -113,7 +113,7 @@ module Homebrew
       end
       unless shellcheck
         opoo "Could not find or install `shellcheck`! Not checking shell style."
-        return !rubocop_success
+        return rubocop_success
       end
 
       shell_files = [
@@ -125,7 +125,7 @@ module Homebrew
       # TODO: check, fix completions here too.
       # TODO: consider using ShellCheck JSON output
       shellcheck_success = system shellcheck, "--shell=bash", *shell_files
-      !rubocop_success || !shellcheck_success
+      rubocop_success && shellcheck_success
     end
 
     class RubocopResults

Library/Homebrew/test/cmd/style_spec.rb

@@ -79,7 +79,7 @@ describe "brew style" do
 
       rubocop_result = Homebrew::Style.check_style_and_print([target_file])
 
-      expect(rubocop_result).to eq false
+      expect(rubocop_result).to eq true
     end
   end
 end

Library/Homebrew/utils/gems.rb

@@ -92,7 +92,7 @@ module Homebrew
     @bundle_installed ||= begin
       bundle = "#{gem_user_bindir}/bundle"
       bundle_check_output = `#{bundle} check 2>&1`
-      bundle_check_failed = !$CHILD_STATUS.exitstatus.zero?
+      bundle_check_failed = !$CHILD_STATUS.success?
 
       # for some reason sometimes the exit code lies so check the output too.
       if bundle_check_failed || bundle_check_output.include?("Install missing gems")