Consolidate errors when loading adapter gem fails into LoadError

If not using Bundler and the specified adapter gem does not exist,
`rubygems` raises `Gem::MissingSpecError`.

`Gem::MissingSpecError` inherits `LoadError`, but the argument of `initialize`
is different.
https://github.com/rubygems/rubygems/blob/9054079ce8a1ad05dd206a3562339b74712c7fc6/lib/rubygems/errors.rb#L27..L31

As a result, `ArugmentError` occurs when re-raising the exception.

Although it is possible to check the error class and specify appropriate
arguments for each of them, I think that it is sufficient to just raise
`LoadError`.

Together, when using Bundler, fixed that gem which error occurred could
not be checked correctly.

Fixes rails#32830.

actioncable/lib/action_cable/server/configuration.rb

@@ -35,15 +35,16 @@ def pubsub_adapter
         rescue LoadError => e
           # We couldn't require the adapter itself. Raise an exception that
           # points out config typos and missing gems.
-          if e.path == path_to_adapter
+          # When `Gem::LoadError` occurs, possible that `path` is not set correctly. Instead can get the gem name from `name` attribute.
+          if (e.path == path_to_adapter) || (e.respond_to?(:name) && e.name == adapter)
             # We can assume that a non-builtin adapter was specified, so it's
             # either misspelled or missing from Gemfile.
-            raise e.class, "Could not load the '#{adapter}' Action Cable pubsub adapter. Ensure that the adapter is spelled correctly in config/cable.yml and that you've added the necessary adapter gem to your Gemfile.", e.backtrace
+            raise LoadError, "Could not load the '#{adapter}' Action Cable pubsub adapter. Ensure that the adapter is spelled correctly in config/cable.yml and that you've added the necessary adapter gem to your Gemfile or installed.", e.backtrace
 
           # Bubbled up from the adapter require. Prefix the exception message
           # with some guidance about how to address it and reraise.
           else
-            raise e.class, "Error loading the '#{adapter}' Action Cable pubsub adapter. Missing a gem it depends on? #{e.message}", e.backtrace
+            raise LoadError, "Error loading the '#{adapter}' Action Cable pubsub adapter. Missing a gem it depends on? #{e.message}", e.backtrace
           end
         end
 

activerecord/lib/active_record/connection_adapters/connection_specification.rb

@@ -191,15 +191,16 @@ def spec(config)
           rescue LoadError => e
             # We couldn't require the adapter itself. Raise an exception that
             # points out config typos and missing gems.
-            if e.path == path_to_adapter
+            # When `Gem::LoadError` occurs, possible that `path` is not set correctly. Instead can get the gem name from `name` attribute.
+            if (e.path == path_to_adapter) || (e.respond_to?(:name) && e.name == spec[:adapter])
               # We can assume that a non-builtin adapter was specified, so it's
               # either misspelled or missing from Gemfile.
-              raise e.class, "Could not load the '#{spec[:adapter]}' Active Record adapter. Ensure that the adapter is spelled correctly in config/database.yml and that you've added the necessary adapter gem to your Gemfile.", e.backtrace
+              raise LoadError, "Could not load the '#{spec[:adapter]}' Active Record adapter. Ensure that the adapter is spelled correctly in config/database.yml and that you've added the necessary adapter gem to your Gemfile or installed.", e.backtrace
 
             # Bubbled up from the adapter require. Prefix the exception message
             # with some guidance about how to address it and reraise.
             else
-              raise e.class, "Error loading the '#{spec[:adapter]}' Active Record adapter. Missing a gem it depends on? #{e.message}", e.backtrace
+              raise LoadError, "Error loading the '#{spec[:adapter]}' Active Record adapter. Missing a gem it depends on? #{e.message}", e.backtrace
             end
           end
 

activerecord/test/cases/connection_specification/resolver_test.rb

@@ -19,7 +19,7 @@ def test_url_invalid_adapter
             spec "ridiculous://foo?encoding=utf8"
           end
 
-          assert_match "Could not load the 'ridiculous' Active Record adapter. Ensure that the adapter is spelled correctly in config/database.yml and that you've added the necessary adapter gem to your Gemfile.", error.message
+          assert_match "Could not load the 'ridiculous' Active Record adapter. Ensure that the adapter is spelled correctly in config/database.yml and that you've added the necessary adapter gem to your Gemfile or installed.", error.message
         end
 
         # The abstract adapter is used simply to bypass the bit of code that