message: Add private methods from tensorflow logging module
diff: @@ -69,13 +69,31 @@ void AWSLogSystem::LogMessage(Aws::Utils::Logging::LogLevel log_level,
  }
  namespace {
  +
  +// Taken from tensorflow/core/platform/default/logging.cc
  +int ParseInteger(const char* str, size_t size) {
  + string integer_str(str, size);
  + std::istringstream ss(integer_str);
  + int level = 0;
  + ss >> level;
  + return level;
  +}
  +
  +// Taken from tensorflow/core/platform/default/logging.cc
  +int64 LogLevelStrToInt(const char* tf_env_var_val) {
  + if (tf_env_var_val == nullptr) {
  + return 0;
  + }
  + return ParseInteger(tf_env_var_val, strlen(tf_env_var_val));
  +}
  +
  static const char* kAWSLoggingTag = "AWSLogging";
  Aws::Utils::Logging::LogLevel ParseLogLevelFromEnv() {
  Aws::Utils::Logging::LogLevel log_level = Aws::Utils::Logging::LogLevel::Info;
  const int64_t level =
  - getenv("AWS_LOG_LEVEL") ? tensorflow::internal::LogLevelStrToInt(getenv("AWS_LOG_LEVEL"))
  + getenv("AWS_LOG_LEVEL") ? LogLevelStrToInt(getenv("AWS_LOG_LEVEL"))
  : tensorflow::internal::MinLogLevelFromEnv();
  switch (level) {
  