roachtest failure: ruby-pg - !!! Installation of ruby 3.1.2 failed!

[smg260]

Since Dec 10, 2022 there have been a number (12 so far) of ruby-pg failures. They are categorised as SSH flakes in #90695 but upon closer inspection seem to happen because ruby cannot be installed for a reason unrelated to SSH.

It is not consistently failing, but frequently enough to warrant some investigation

/usr/local/src/ruby-3.1.2/lib/rubygems/installer.rb:272:in `check_executable_overwrite': "erb" from erb conflicts with /usr/local/bin/erb (Gem::InstallError)
	from ./tool/rbinstall.rb:868:in `check_executable_overwrite'
	from /usr/local/src/ruby-3.1.2/lib/rubygems/installer.rb:513:in `block in generate_bin'
	from /usr/local/src/ruby-3.1.2/lib/rubygems/installer.rb:492:in `each'
	from /usr/local/src/ruby-3.1.2/lib/rubygems/installer.rb:492:in `generate_bin'
	from /usr/local/src/ruby-3.1.2/lib/rubygems/installer.rb:333:in `install'
	from ./tool/rbinstall.rb:899:in `block in install'
	from ./tool/rbinstall.rb:713:in `no_write'
	from ./tool/rbinstall.rb:899:in `install'
	from ./tool/rbinstall.rb:1002:in `block in install_default_gem'
	from ./tool/rbinstall.rb:989:in `each'
	from ./tool/rbinstall.rb:989:in `install_default_gem'
	from ./tool/rbinstall.rb:927:in `block in <main>'
	from ./tool/rbinstall.rb:1127:in `block in <main>'
	from ./tool/rbinstall.rb:1124:in `each'
	from ./tool/rbinstall.rb:1124:in `<main>'
make: *** [uncommon.mk:383: do-install-all] Error 1
!!! Installation of ruby 3.1.2 failed!

2 issues:

• ruby is failing installation
• this is categorised as an SSH flake

Jira issue: CRDB-23268

[blathers-crl]

cc @cockroachdb/test-eng

[smg260]

@rafiss have you seen this error before? It was happening fairly frequently, though the last time was on March 4th.
(I see #97314 is on your radar already)

[rafiss]

I haven't seen, or more accurately, noticed, this type of failure before. I have an idea though. We probably should clean up /usr/local/bin/erb at the beginning of this test, since it looks like gem doesn't like it if you install something that's there already.