Clarified error message about missing python modules, and tweak documentation to suggest overriding interpreter.

plugins/doc_fragments/mysql.py

@@ -80,8 +80,10 @@ notes:
      yum install python2-PyMySQL (RHEL/CentOS/Fedora; see M(ansible.builtin.yum)). You can also use dnf install python2-PyMySQL
      for newer versions of Fedora; see M(ansible.builtin.dnf).
    - Be sure you have PyMySQL or MySQLdb library installed on the target machine
-     for the Python interpreter Ansible uses, for example, if it is Python 3,
-     you must install the library for Python 3. You can also change the interpreter.
+     for the Python interpreter Ansible discovers.  For example if ansible discovers and uses Python 3, you need to install
+     the Python 3 version of PyMySQL.  If ansible discovers and uses Python 2, you need to install the Python 2 version
+     of either PyMySQL or MySQL-python.
+   - If you have trouble, it may help to force Ansible to use Python 3 by specifying C(ansible_python_interpreter).
      For more information, see U(https://docs.ansible.com/ansible/latest/reference_appendices/interpreter_discovery.html).
    - Both C(login_password) and C(login_user) are required when you are
      passing credentials. If none are present, the module will attempt to read

plugins/module_utils/mysql.py

@@ -29,7 +29,7 @@ except ImportError:
     except ImportError:
         mysql_driver = None
 
-mysql_driver_fail_msg = 'The PyMySQL (Python 2.7 and Python 3.X) or MySQL-python (Python 2.X) module is required.'
+mysql_driver_fail_msg = 'A MySQL module is required: for Python 2.7 either PyMySQL or MySQL-python, or for Python 3.X PyMySQL.  Consider setting ansible_python_interpreter to use the intended Python version.'
 
 
 def parse_from_mysql_config_file(cnf):