fix some copy options re unknown indexes

tests/NRediSearch.Test/ClientTests/ClientTest.cs

@@ -50,7 +50,9 @@ public void Search()
             Assert.True(cl.DropIndex());
 
             var ex = Assert.Throws<RedisServerException>(() => cl.Search(new Query("hello world")));
-            Assert.Equal("Unknown Index name", ex.Message, ignoreCase: true);
+            Assert.True(
+                string.Equals("Unknown Index name", ex.Message, System.StringComparison.InvariantCultureIgnoreCase)
+                || string.Equals("no such index", ex.Message, System.StringComparison.InvariantCultureIgnoreCase));
         }
 
         [Fact]
@@ -557,7 +559,9 @@ public void TestDropMissing()
         {
             Client cl = GetClient();
             var ex = Assert.Throws<RedisServerException>(() => cl.DropIndex());
-            Assert.Equal("Unknown Index name", ex.Message, ignoreCase: true);
+            Assert.True(
+                string.Equals("Unknown Index name", ex.Message, System.StringComparison.InvariantCultureIgnoreCase)
+                || string.Equals("no such index", ex.Message, System.StringComparison.InvariantCultureIgnoreCase));
         }
 
         [Fact]

tests/NRediSearch.Test/RediSearchTestBase.cs

@@ -38,7 +38,15 @@ protected static Client Reset(Client client)
             }
             catch (RedisServerException ex)
             {
-                if (!string.Equals(ex.Message, "Unknown Index name", StringComparison.OrdinalIgnoreCase)) throw;
+                if (string.Equals("Unknown Index name", ex.Message, System.StringComparison.InvariantCultureIgnoreCase)
+                    || string.Equals("no such index", ex.Message, System.StringComparison.InvariantCultureIgnoreCase))
+                {
+                    // fine
+                }
+                else
+                {
+                    throw;
+                }
             }
             return client;
         }