Add error specs for BodyWrapper close method

I noticed I broke something earlier while writing the previous commit in
the close method, but it didn't fail any specs. That's because there
weren't any for the error reporting. Add these errors so we can be sure
it works.

spec/lib/appsignal/rack/body_wrapper_spec.rb

@@ -113,6 +113,43 @@
 
       expect(transaction).to include_event("name" => "close_response_body.rack")
     end
+
+    it "reports an error if an error occurs on close" do
+      fake_body = double
+      expect(fake_body).to receive(:close).and_raise(ExampleException, "error message")
+
+      wrapped = described_class.wrap(fake_body, transaction)
+      expect do
+        wrapped.close
+      end.to raise_error(ExampleException, "error message")
+
+      expect(transaction).to have_error("ExampleException", "error message")
+    end
+
+    it "doesn't report EPIPE error on close" do
+      fake_body = double
+      expect(fake_body).to receive(:close).and_raise(Errno::EPIPE)
+
+      wrapped = described_class.wrap(fake_body, transaction)
+      expect do
+        wrapped.close
+      end.to raise_error(Errno::EPIPE)
+
+      expect(transaction).to_not have_error
+    end
+
+    it "does not report EPIPE error when it's the error cause on close" do
+      error = error_with_cause(StandardError, "error message", Errno::EPIPE)
+      fake_body = double
+      expect(fake_body).to receive(:close).and_raise(error)
+
+      wrapped = described_class.wrap(fake_body, transaction)
+      expect do
+        wrapped.close
+      end.to raise_error(StandardError, "error message")
+
+      expect(transaction).to_not have_error
+    end
   end
 
   describe "with a body supporting both each() and call" do