Replacing NotNullAttribute with thrown exceptions

src/Microsoft.AspNet.WebSockets.Client/project.json

@@ -5,6 +5,9 @@
         "type": "git",
         "url": "git://github.com/aspnet/websockets"
     },
+    "compilationOptions": {
+        "warningsAsErrors": true
+    },
     "dependencies": {
         "Microsoft.AspNet.WebSockets.Protocol": "1.0.0-*"
     },

src/Microsoft.AspNet.WebSockets.Protocol/HandshakeHelpers.cs

@@ -5,7 +5,6 @@ using System;
 using System.Collections.Generic;
 using System.Security.Cryptography;
 using System.Text;
-using Microsoft.Extensions.Internal;
 
 namespace Microsoft.AspNet.WebSockets.Protocol
 {
@@ -124,8 +123,13 @@ namespace Microsoft.AspNet.WebSockets.Protocol
         /// </summary>
         /// <param name="requestKey"></param>
         /// <returns></returns>
-        public static string CreateResponseKey([NotNull] string requestKey)
+        public static string CreateResponseKey(string requestKey)
         {
+            if (requestKey == null)
+            {
+                throw new ArgumentNullException(nameof(requestKey));
+            }
+
             using (var algorithm = SHA1.Create())
             {
                 string merged = requestKey + "258EAFA5-E914-47DA-95CA-C5AB0DC85B11";

src/Microsoft.AspNet.WebSockets.Protocol/project.json

@@ -5,8 +5,8 @@
         "type": "git",
         "url": "git://github.com/aspnet/websockets"
     },
-    "dependencies": {
+    "compilationOptions": {
-        "Microsoft.Extensions.NotNullAttribute.Sources": { "type": "build", "version": "1.0.0-*" }
+        "warningsAsErrors": true
     },
     "frameworks": {
         "net45": { },

test/Microsoft.AspNet.WebSockets.Protocol.Test/BufferStream.cs

@@ -7,7 +7,6 @@ using System.Diagnostics.Contracts;
 using System.IO;
 using System.Threading;
 using System.Threading.Tasks;
-using Microsoft.Extensions.Internal;
 
 namespace Microsoft.AspNet.WebSockets.Protocol.Test
 {
@@ -256,7 +255,7 @@ namespace Microsoft.AspNet.WebSockets.Protocol.Test
             return Task.FromResult<object>(null);
         }
 
-        private static void VerifyBuffer([NotNull] byte[] buffer, int offset, int count, bool allowEmpty)
+        private static void VerifyBuffer(byte[] buffer, int offset, int count, bool allowEmpty)
         {
             if (offset < 0 || offset > buffer.Length)
             {

test/Microsoft.AspNet.WebSockets.Protocol.Test/project.json

@@ -1,7 +1,6 @@
 {
     "dependencies": {
         "Microsoft.AspNet.WebSockets.Protocol": "1.0.0-*",
-        "Microsoft.Extensions.NotNullAttribute.Sources": { "type": "build", "version": "1.0.0-*" },
         "xunit.runner.aspnet": "2.0.0-aspnet-*"
     },
     "frameworks": {