Check if safe_load is defined on YAML before using it

Gemfile

@@ -64,6 +64,7 @@ gem 'sidekiq', require: nil
 gem 'simplecov', require: false
 gem 'simplecov-cobertura', require: false
 gem 'sucker_punch', '~> 2.0', require: nil
+gem 'syck', require: nil if !defined?(JRUBY_VERSION)
 gem 'yard', require: nil
 gem 'yarjuf'
 
@@ -125,10 +126,8 @@ if RUBY_PLATFORM == 'java'
   end
 elsif frameworks_versions['rails'] =~ /^(4|5)/
   gem 'sqlite3', '~> 1.3.6'
-elsif RUBY_VERSION < '2.7'
-  gem 'sqlite3', '~> 1.4.4'
 else
-  gem 'sqlite3'
+  gem 'sqlite3', '~> 1.4.4'
 end
 
 # sneakers main only supports >=2.5.0

lib/elastic_apm/config.rb

@@ -256,7 +256,7 @@ def load_config_file
 
       read = File.read(config_file)
       evaled = ERB.new(read).result
-      YAML.safe_load(evaled)
+      YAML.method_defined?(:safe_load) ? YAML.safe_load(evaled) : YAML.load(evaled)
     end
 
     def load_env

spec/integration/syck_spec.rb

@@ -0,0 +1,31 @@
+# Licensed to Elasticsearch B.V. under one or more contributor
+# license agreements. See the NOTICE file distributed with
+# this work for additional information regarding copyright
+# ownership. Elasticsearch B.V. licenses this file to you under
+# the Apache License, Version 2.0 (the "License"); you may
+# not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+
+# frozen_string_literal: true
+
+if !defined?(JRUBY_VERSION)
+  require 'integration_helper'
+  require 'syck'
+
+  RSpec.describe 'Syck YAML' do
+
+    it 'loads from config file' do
+      config = ElasticAPM::Config.new(config_file: 'spec/fixtures/elastic_apm.yml')
+      expect(config.server_url).to eq 'somewhere-config.com'
+    end
+  end
+end