Warnings should be on by default in unittest so that developers can see them while running the tests even if they are silenced by default in Python.

The plan is to add a "warnings" argument to TestProgram and the default TextTestRunner:
  * if the argument is passed always use it as a filter (e.g. default, ignore, all, ...) for warnings;
  * if the argument is not passed and sys.warnoptions is not [] (i.e. python has been called with "-W something") don't do anything (i.e. use the warnings specified by -W);
  * if the argument is not passed and sys.warnoptions is [], use 'default' (i.e. show warnings).

In order to prevent floods of warnings when the deprecated assertEquals, assert_, etc. are used (see #9424), a new type of warning could be created (e.g. _UnittestDeprecationWarning) and filtered so that these warnings are printed only once.