ruby gem load error: cannot load such file -- google/2.6/protobuf_c with ruby 2.6.1p33

[directionless]

This appears to be a recurrence of #3509

Folks have commented there, but it seems worth bringing this into it's own ticket.

I'm running on macosx, ruby 2.6.1. And I see this problem with google-protobuf 2.6.0, 2.6.1, and 3.5.1.2.

Notably, I can load the gem fine with 3.7.0.rc.2

$ ruby --version
ruby 2.6.1p33 (2019-01-30 revision 66950) [x86_64-darwin17]

$ bundle exec ruby -e 'require "google/protobuf"; puts "hi"'
Traceback (most recent call last):
	3: from -e:1:in `<main>'
	2: from -e:1:in `require'
	1: from /Users/seph/.rbenv/versions/2.6.1/lib/ruby/gems/2.6.0/gems/google-protobuf-3.6.1-universal-darwin/lib/google/protobuf.rb:48:in `<top (required)>'
/Users/seph/.rbenv/versions/2.6.1/lib/ruby/gems/2.6.0/gems/google-protobuf-3.6.1-universal-darwin/lib/google/protobuf.rb:48:in `require': cannot load such file -- google/2.6/protobuf_c (LoadError)
	4: from -e:1:in `<main>'
	3: from -e:1:in `require'
	2: from /Users/seph/.rbenv/versions/2.6.1/lib/ruby/gems/2.6.0/gems/google-protobuf-3.6.1-universal-darwin/lib/google/protobuf.rb:47:in `<top (required)>'
	1: from /Users/seph/.rbenv/versions/2.6.1/lib/ruby/gems/2.6.0/gems/google-protobuf-3.6.1-universal-darwin/lib/google/protobuf.rb:50:in `rescue in <top (required)>'
/Users/seph/.rbenv/versions/2.6.1/lib/ruby/gems/2.6.0/gems/google-protobuf-3.6.1-universal-darwin/lib/google/protobuf.rb:50:in `require': cannot load such file -- google/protobuf_c (LoadError)

[TeBoring]

I guess the problem is, before 3.7.0.rc.2, we never supported ruby 2.6.
Thus, for ruby 2.6, you have to use protobuf 3.7

[KLCrow]

I have the same error:
ruby-2.7.3
rails (4.2.11.1)
google-protobuf (3.15.8)
grpc (1.31.1)
cannot load such file -- ..._pb (LoadError)