Added support for FAIL_PRY which will make pry raise a RuntimeError if it is called with that env variable present

lib/pry/pry_class.rb

@@ -161,6 +161,9 @@ you can add "Pry.config.windows_console_warning = false" to your .pryrc.
   #   Pry.start(Object.new, :input => MyInput.new)
   def self.start(target=nil, options={})
     return if ENV['DISABLE_PRY']
+    if ENV['FAIL_PRY']
+      raise 'You have FAIL_PRY set to true, which results in Pry calls failing'
+    end
     options = options.to_hash
 
     if in_critical_section?

spec/pry_spec.rb

@@ -42,6 +42,24 @@ describe Pry do
     end
   end
 
+  describe 'FAIL_PRY' do
+    before do
+      ENV['FAIL_PRY'] = 'true'
+    end
+
+    after do
+      ENV.delete 'FAIL_PRY'
+    end
+
+    it 'should raise an error for binding.pry' do
+      expect{binding.pry}.to raise_error(RuntimeError)
+    end
+
+    it 'should raise an error for Pry.start' do
+      expect{Pry.start}.to raise_error(RuntimeError)
+    end
+  end
+
   describe "Pry.critical_section" do
     it "should prevent Pry being called" do
       output = StringIO.new