On macOS 10.15.7, installed from homebrew, I see this:
% travis monitor Traceback (most recent call last):
18: from /usr/local/Cellar/travis/1.10.0/libexec/bin/travis:23:in `<main>'
17: from /usr/local/Cellar/travis/1.10.0/libexec/bin/travis:23:in `load'
16: from /usr/local/Cellar/travis/1.10.0/libexec/gems/travis-1.10.0/bin/travis:18:in `<top (required)>'
15: from /usr/local/Cellar/travis/1.10.0/libexec/gems/travis-1.10.0/lib/travis/cli.rb:62:in `run'
14: from /usr/local/Cellar/travis/1.10.0/libexec/gems/travis-1.10.0/lib/travis/cli.rb:69:in `command'
13: from /usr/local/Cellar/travis/1.10.0/libexec/gems/travis-1.10.0/lib/travis/cli.rb:69:in `const_get'
12: from /usr/local/Cellar/ruby/2.7.2/lib/ruby/2.7.0/rubygems/core_ext/kernel_require.rb:72:in `require'
11: from /usr/local/Cellar/ruby/2.7.2/lib/ruby/2.7.0/rubygems/core_ext/kernel_require.rb:72:in `require'
10: from /usr/local/Cellar/travis/1.10.0/libexec/gems/travis-1.10.0/lib/travis/cli/monitor.rb:2:in `<top (required)>'
9: from /usr/local/Cellar/ruby/2.7.2/lib/ruby/2.7.0/rubygems/core_ext/kernel_require.rb:72:in `require'
8: from /usr/local/Cellar/ruby/2.7.2/lib/ruby/2.7.0/rubygems/core_ext/kernel_require.rb:72:in `require'
7: from /usr/local/Cellar/travis/1.10.0/libexec/gems/travis-1.10.0/lib/travis/tools/notification.rb:6:in `<top (required)>'
6: from /usr/local/Cellar/travis/1.10.0/libexec/gems/travis-1.10.0/lib/travis/tools/notification.rb:7:in `<module:Travis>'
5: from /usr/local/Cellar/travis/1.10.0/libexec/gems/travis-1.10.0/lib/travis/tools/notification.rb:8:in `<module:Tools>'
4: from /usr/local/Cellar/travis/1.10.0/libexec/gems/travis-1.10.0/lib/travis/tools/notification.rb:26:in `<module:Notification>'
3: from /usr/local/Cellar/travis/1.10.0/libexec/gems/travis-1.10.0/lib/travis/tools/notification.rb:27:in `<class:Dummy>'
2: from /usr/local/Cellar/travis/1.10.0/libexec/gems/travis-1.10.0/lib/travis/tools/assets.rb:9:in `asset_path'
1: from /usr/local/Cellar/travis/1.10.0/libexec/gems/travis-1.10.0/lib/travis/tools/assets.rb:9:in `tap'
/usr/local/Cellar/travis/1.10.0/libexec/gems/travis-1.10.0/lib/travis/tools/assets.rb:10:in `block in asset_path': Travis CI.app/Contents/MacOS/Travis CI (Travis::Client::AssetNotFound)
I can also reproduce using gem to install with the system Ruby (2.6.0).
On macOS 10.15.7, installed from homebrew, I see this:
I can also reproduce using gem to install with the system Ruby (2.6.0).