Fix for environment without git

Author: nobu

tempfile.gemspec

@@ -23,7 +23,7 @@ Gem::Specification.new do |spec|
   # Specify which files should be added to the gem when it is released.
   # The `git ls-files -z` loads the files in the RubyGem that have been added into git.
   gemspec = File.basename(__FILE__)
-  spec.files = IO.popen(%w[git ls-files -z], chdir: __dir__, err: IO::NULL) do |ls|
+  spec.files = IO.popen(%w[git ls-files -z], chdir: __dir__, err: IO::NULL, exception: false) do |ls|
     ls.readlines("\x0", chomp: true).reject do |f|
       (f == gemspec) ||
         f.start_with?(*%w[bin/ test/ spec/ features/ .git Gemfile])