Migrate to C++17 and misc code cleanups

Change-Id: I6b63385c92361a7ef5803d2bfd00f39c77e88d34
diff --git a/tests/identity-management-fixture.cpp b/tests/identity-management-fixture.cpp
index 681e076..ef5ab5c 100644
--- a/tests/identity-management-fixture.cpp
+++ b/tests/identity-management-fixture.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
-/**
- * Copyright (c) 2014-2020, Regents of the University of California.
+/*
+ * Copyright (c) 2014-2022, Regents of the University of California.
  *
  * This file is part of NDN repo-ng (Next generation of NDN repository).
  * See AUTHORS.md for complete list of repo-ng authors and contributors.
@@ -18,15 +18,16 @@
  */
 
 #include "identity-management-fixture.hpp"
+
 #include <ndn-cxx/security/pib/identity.hpp>
 #include <ndn-cxx/security/pib/key.hpp>
 #include <ndn-cxx/security/pib/pib.hpp>
 #include <ndn-cxx/security/certificate.hpp>
 #include <ndn-cxx/util/io.hpp>
+
 #include <boost/filesystem.hpp>
 
-namespace repo {
-namespace tests {
+namespace repo::tests {
 
 IdentityManagementFixture::IdentityManagementFixture()
   : m_keyChain("pib-memory:", "tpm-memory:")
@@ -78,5 +79,4 @@
   }
 }
 
-} // namespace tests
-} // namespace repo
+} // namespace repo::tests