private RegionMetadata loadFromSystemProperty() {
        final String overrideFilePath = System.getProperty
                (REGIONS_FILE_OVERRIDE);

        if (overrideFilePath != null) {
            try {
                return LegacyRegionXmlLoadUtils.load(new File
                        (overrideFilePath));
            } catch (IOException exception) {
                throw new SdkClientException(
                        "Error parsing region metadata from " + overrideFilePath,
                        exception);
            }
        }
        return null;
    }
Loads region metadata from file location specified in
{@link #REGIONS_FILE_OVERRIDE} property.
Returns null if no such property exists.

@throws SdkClientException if any error occurs while loading the
                              metadata file.
aws-java-sdk-core/src/main/java/com/amazonaws/regions/LegacyRegionXmlMetadataBuilder.java