Resolve CI Setup Failure

[seanreinhardtapps]

From CI runs on PR #96, I noticed failed builds from packages installed by rvm use when setting up test runs for ruby-2.0.0-p648 and ruby-2.3.4.

Example failed setup: https://travis-ci.org/github/CocoaPods/cocoapods-downloader/jobs/673912761#L743

I'm not sure if there's a preference regarding running the tests on MacOS or Linux, but there is a linux distribution: dist: trusty setting in the config, so I thought I'd try running the tests on linux.

[seanreinhardtapps]

I understand now that this gem is built to run on MacOS, as it supports DMGs using hdiutil.
I believe the error I've seen installing the two ruby versions are along the lines of: travis-ci/travis-rubies#68

To continue supporting ruby-2.0.0-p648 and ruby-2.3.4, we might have to look into installing an older version of openssl.

[amorde]

is the issue with bzr? is homebrew not installing the correct version of openssl?

[seanreinhardtapps]

@amorde the failure is early in the agent setup, resultant of dependencies installation from the rvm use invocation. This point in the agent setup seems to be before any of the test case configuration.
The two failing cases are trying to install binary ruby version hosted by Travis CI, which are not available any longer from RVM.

The actual error is a symlink error (failed brew link) linking an installed Python version required by pkg-config. Example: https://travis-ci.org/github/CocoaPods/cocoapods-downloader/jobs/673912762#L529

What is the priority level on continuing to test these end of life ruby versions?

[seanreinhardtapps]

Summary:

• RVM installation of ruby 2.3.x or lower on Travis-CI High Sierra + VMs fails, unrelated to the cocoapods-downloader config.
• Specifying a Sierra version allow testing to continue on these versions.
• When specifying versions, I ran into failed svn tests on Catalina Agents, since Xcode command line tools do not install command line svn by default any longer. See
  https://developer.apple.com/documentation/macos_release_notes/macos_catalina_10_15_release_notes?language=objc
  https://stackoverflow.com/questions/60869347/mac-command-line-tools-11-4-no-longer-has-svn
• Using Homebrew to install the svn command line utility works for Catalina VMs. It should be noted that this could be considered hiding a problem for CocoaPods users who haven't installed the Xcode command line tools, I haven't had an opportunity to dig into it further.

[amorde]

Sound like we should potentially add a warning to download svn when encountering a source that has it and svn isn't available. That's out of scope for this PR though.

[amorde]

Thank you for investigating this and for fixing it 🙏