Trying to build on macOS and I get the following error:

[7sharp9]

I have included the full text but in brief this is the error:

➜ cmake --build ./build --config Release
[  4%] Building CXX object _deps/trainers-build/src/CMakeFiles/TrainingTools.dir/src/Error.cpp.o
[  4%] Building CXX object _deps/trainers-build/src/CMakeFiles/TrainingTools.dir/src/ModelAware.cpp.o
[  8%] Building CXX object _deps/trainers-build/src/CMakeFiles/TrainingTools.dir/src/iterative/IterationsAware.cpp.o
/Users/davethomas/GitHub/GaussianProcesses/build/_deps/trainers-src/src/src/iterative/IterationsAware.cpp:14:11: error: no matching conversion for functional-style cast from 'const char[19]' to 'Error'
    throw Error("Too few iterations");
          ^~~~~~~~~~~~~~~~~~~~~~~~~~
/Users/davethomas/GitHub/GaussianProcesses/build/_deps/trainers-src/src/header/TrainingTools/Error.h:13:7: note: candidate constructor (the implicit copy constructor) not viable: no known conversion from 'const char[19]' to 'const train::Error' for 1st argument
class Error : public std::runtime_error {
      ^
/Users/davethomas/GitHub/GaussianProcesses/build/_deps/trainers-src/src/header/TrainingTools/Error.h:13:7: note: candidate constructor (the implicit move constructor) not viable: no known conversion from 'const char[19]' to 'train::Error' for 1st argument
/Users/davethomas/GitHub/GaussianProcesses/build/_deps/trainers-src/src/header/TrainingTools/Error.h:15:12: note: candidate constructor not viable: no known conversion from 'const char[19]' to 'const std::string' (aka 'const basic_string<char>') for 1st argument
  explicit Error(const std::string &what);
           ^
1 error generated.
make[2]: *** [_deps/trainers-build/src/CMakeFiles/TrainingTools.dir/src/iterative/IterationsAware.cpp.o] Error 1
make[1]: *** [_deps/trainers-build/src/CMakeFiles/TrainingTools.dir/all] Error 2
make: *** [all] Error 2

error.txt

What have I missed?