backslash not available under cygwin with french keyboard.

With 40297, one character seams to be unavailable from French keyboard:

After installing cygwin (with error (see CORE-4026)),
I launched cmd.exe.

Then, backslash () is available combining [Alt Gr]+[_8]

Then, I cd to \cygwin\bin and launch bash.exe

Then, backslash () is not available anymore by combining [Alt Gr]+[_8], when for other characters status in unclear.

For example,

combining [Alt Gr]+[(5], makes a correct '[' none of first time, but each second time.

combining [Alt Gr]+["3], makes a correct '#' each time, but this # is directly followed by an unexpected new line character.