Show logs in case of Mkdir or Rmdir failures in wxFSW unit tests

Try to gather more information about the test failures on GitHub Actions
when creating or removing the test directory that isn't reproducible
locally.

tests/fswatcher/fswatchertest.cpp

@@ -23,6 +23,7 @@
 #include "wx/filename.h"
 #include "wx/filefn.h"
 #include "wx/fswatcher.h"
+#include "wx/log.h"
 #include "wx/scopedptr.h"
 #include "wx/stdpaths.h"
 #include "wx/vector.h"
@@ -33,6 +34,27 @@
 // local functions
 // ----------------------------------------------------------------------------
 
+#if wxUSE_LOG
+// Logging is disabled by default when running the tests, but sometimes it can
+// be helpful to see the errors in case of unexpected failure, so this class
+// re-enables logs in its scope.
+//
+// It's a counterpart to wxLogNull.
+class LogEnabler
+{
+public:
+    LogEnabler() : m_wasEnabled(wxLog::EnableLogging(true)) { }
+    ~LogEnabler() { wxLog::EnableLogging(m_wasEnabled); }
+
+private:
+    const bool m_wasEnabled;
+
+    wxDECLARE_NO_COPY_CLASS(LogEnabler);
+};
+#else // !wxUSE_LOG
+class LogEnabler { };
+#endif // wxUSE_LOG/!wxUSE_LOG
+
 // class generating file system events
 class EventGenerator
 {
@@ -138,7 +160,10 @@ public:
         // unique filename, the file always get created...
         ms_watchDir.AppendDir("fswatcher_test");
         REQUIRE(!ms_watchDir.DirExists());
+
+        LogEnabler enableLogs;
         REQUIRE(ms_watchDir.Mkdir());
+
         REQUIRE(ms_watchDir.DirExists());
 
         return ms_watchDir;
@@ -151,6 +176,7 @@ public:
         // just to be really sure we know what we remove
         REQUIRE( ms_watchDir.GetDirs().Last() == "fswatcher_test" );
 
+        LogEnabler enableLogs;
         CHECK( ms_watchDir.Rmdir(wxPATH_RMDIR_RECURSIVE) );
 
         ms_watchDir = wxFileName();