fix SecurityError: Insecure operation - gem_original_require`

[takkanm]

I noticed that test on Ruby 2.7 failed, because raised SecurityError.

https://travis-ci.org/tzinfo/tzinfo/jobs/526594506

  1) Error:
TCTimezone#test_get_tainted_and_frozen_not_previously_loaded:
SecurityError: Insecure operation - require
    /home/travis/build/tzinfo/tzinfo/lib/tzinfo/data_sources/ruby_data_source.rb:129:in `require'
    /home/travis/build/tzinfo/tzinfo/lib/tzinfo/data_sources/ruby_data_source.rb:129:in `require_data'
    /home/travis/build/tzinfo/tzinfo/lib/tzinfo/data_sources/ruby_data_source.rb:115:in `require_definition'
    /home/travis/build/tzinfo/tzinfo/lib/tzinfo/data_sources/ruby_data_source.rb:93:in `load_timezone_info'
    /home/travis/build/tzinfo/tzinfo/lib/tzinfo/data_source.rb:195:in `get_timezone_info'
    /home/travis/build/tzinfo/tzinfo/lib/tzinfo/timezone.rb:128:in `get'
    /home/travis/build/tzinfo/tzinfo/test/tc_timezone.rb:291:in `block in test_get_tainted_and_frozen_not_previously_loaded'
    /home/travis/build/tzinfo/tzinfo/test/test_utils.rb:311:in `block in safe_test'

[philr]

I'd prefer to handle the untainting before the require_data method gets called. The file name gets validated and replaced with a known to be safe string in the load_timezone_info method. I assume the source of the SecurityError is therefore the @base_path.

Could you check this assumption is true and move the untaint call to whichever branch of the initializer is causing the problem?

[takkanm]

@philr I'll try it.

[takkanm]

I fixed it.