From https://msdn.microsoft.com/en-us/library/windows/desktop/ms682425.aspx

Note Python is using CreateProcess(), consider using CreateProcessW()

The Unicode version of this function, CreateProcessW, can modify the contents of this string. Therefore, this parameter cannot be a pointer to read-only memory (such as a const variable or a literal string). If this parameter is a constant string, the function may cause an access violation.