message: pcm-iio: make error output more user friendly suggesting a solution
  If event file is not found the following string is output:
  event file opCode.txt or/usr/share/pcm/opCode.txt is not avaiable. Copy it from PCM build directory.
diff: @@ -339,10 +339,12 @@ vector<struct counter> load_events(const char* fn)
  if (!in.is_open())
  {
  - in.open(std::string("/usr/share/pcm/") + fn);
  + const auto alt_fn = std::string("/usr/share/pcm/") + fn;
  + in.open(alt_fn);
  if (!in.is_open())
  {
  - throw std::invalid_argument("event file is not avaiable. In the future version, we will load a preset");
  + const auto err_msg = std::string("event file ") + fn + " or " + alt_fn + " is not avaiable. Copy it from PCM build directory.";
  + throw std::invalid_argument(err_msg);
  }
  }
  