public static String getPrivateKey(String fileName) {
		Assert.hasText(fileName, "fileName must not be empty nor null");
		isFilePresent(fileName);
		try {
			return FileCopyUtils.copyToString(new FileReader(fileName));
		}
		catch (final IOException e) {
			throw new IllegalStateException(e);
		}
	}
Retrieves the private key from a file, so we can execute commands on the container.

@param fileName The location of the private key file
@return The private key
spring-xd-integration-test/src/main/java/org/springframework/xd/integration/util/ConfigUtil.java