std::experimental::filesystem::filesystem_error::what
From cppreference.com
                    
                                        
                    < cpp | experimental | fs | filesystem error
                    
                                                            
                    | const char* what() const; | (filesystem TS) | |
Returns the explanatory byte string that was stored in the exception object.
Parameters
(none)
Exceptions
noexcept specification:  
noexcept
  See also
| This section is incomplete |