updates

Author: MarcoRossignoli

src/coverlet.core/Helpers/InstrumentationHelper.cs

@@ -97,7 +97,7 @@ public static void BackupOriginalModule(string module, string identifier)
             File.Copy(module, backupPath, true);
             if (!_backupList.TryAdd(module, backupPath))
             {
-                throw new ArgumentException($"Key already found '{module}'");
+                throw new ArgumentException($"Key already added '{module}'");
             }
 
             var symbolFile = Path.ChangeExtension(module, ".pdb");
@@ -106,7 +106,7 @@ public static void BackupOriginalModule(string module, string identifier)
                 File.Copy(symbolFile, backupSymbolPath, true);
                 if (!_backupList.TryAdd(symbolFile, backupSymbolPath))
                 {
-                    throw new ArgumentException($"Key already found '{module}'");
+                    throw new ArgumentException($"Key already added '{module}'");
                 }
             }
         }