make contentRootMissing exception more meaningful

Author: infeo

src/main/java/org/cryptomator/cryptofs/ContentRootMissingException.java

@@ -1,10 +1,11 @@
 package org.cryptomator.cryptofs;
 
 import java.nio.file.NoSuchFileException;
+import java.nio.file.Path;
 
 public class ContentRootMissingException extends NoSuchFileException {
 
-	public ContentRootMissingException(String msg) {
-		super(msg);
+	public ContentRootMissingException(Path encryptedVaultRootDir) {
+		super(encryptedVaultRootDir.toString());
 	}
 }

src/main/java/org/cryptomator/cryptofs/CryptoFileSystems.java

@@ -76,7 +76,7 @@ private void checkVaultRootExistence(Path pathToVault, Cryptor cryptor) throws C
 		String dirHash = cryptor.fileNameCryptor().hashDirectoryId(Constants.ROOT_DIR_ID);
 		Path vaultCipherRootPath = pathToVault.resolve(Constants.DATA_DIR_NAME).resolve(dirHash.substring(0, 2)).resolve(dirHash.substring(2));
 		if (!Files.exists(vaultCipherRootPath)) {
-			throw new ContentRootMissingException("The encrypted root directory of the vault " + pathToVault + " is missing.");
+			throw new ContentRootMissingException(vaultCipherRootPath);
 		}
 	}