Use string interpolation for error messages.

Author: Tratcher

src/Microsoft.AspNet.Http/Authentication/DefaultAuthenticationManager.cs

@@ -58,7 +58,7 @@ public override AuthenticationResult Authenticate([NotNull] string authenticatio
 
             if (!authenticateContext.Accepted)
             {
-                throw new InvalidOperationException("The following authentication scheme was not accepted: " + authenticationScheme);
+                throw new InvalidOperationException($"The following authentication scheme was not accepted: {authenticationScheme}");
             }
 
             return new AuthenticationResult(authenticateContext.Principal,
@@ -79,7 +79,7 @@ public override async Task<AuthenticationResult> AuthenticateAsync([NotNull] str
             // Verify all types ack'd
             if (!authenticateContext.Accepted)
             {
-                throw new InvalidOperationException("The following authentication scheme was not accepted: " + authenticationScheme);
+                throw new InvalidOperationException($"The following authentication scheme was not accepted: {authenticationScheme}");
             }
 
             return new AuthenticationResult(authenticateContext.Principal,
@@ -101,7 +101,7 @@ public override void Challenge(AuthenticationProperties properties, string authe
             // The default Challenge with no scheme is always accepted
             if (!challengeContext.Accepted && !string.IsNullOrEmpty(authenticationScheme))
             {
-                throw new InvalidOperationException("The following authentication type was not accepted: " + authenticationScheme);
+                throw new InvalidOperationException($"The following authentication scheme was not accepted: {authenticationScheme}");
             }
         }
 
@@ -118,7 +118,7 @@ public override void SignIn([NotNull] string authenticationScheme, [NotNull] Cla
             // Verify all types ack'd
             if (!signInContext.Accepted)
             {
-                throw new InvalidOperationException("The following authentication scheme was not accepted: " + authenticationScheme);
+                throw new InvalidOperationException($"The following authentication scheme was not accepted: {authenticationScheme}");
             }
         }
 
@@ -135,7 +135,7 @@ public override void SignOut(string authenticationScheme, AuthenticationProperti
             // Verify all types ack'd
             if (!string.IsNullOrWhiteSpace(authenticationScheme) && !signOutContext.Accepted)
             {
-                throw new InvalidOperationException("The following authentication scheme was not accepted: " + authenticationScheme);
+                throw new InvalidOperationException($"The following authentication scheme was not accepted: {authenticationScheme}");
             }
         }