Remove warning filtering in iptest.

IPython/testing/iptest.py

@@ -46,15 +46,6 b' pjoin = path.join'
 # Enable printing all warnings raise by IPython's modules
 warnings.filterwarnings('default', message='.*', category=Warning, module='IPy.*')
 
-
-if version_info < (4,2):
-    # ignore some warnings from traitlets until 6.0
-    warnings.filterwarnings('ignore', message='.*on_trait_change is deprecated: use observe instead.*')
-    warnings.filterwarnings('ignore', message='.*was set from the constructor.*', category=Warning, module='IPython.*')
-    warnings.filterwarnings('ignore', message='.*use the instance .help string directly, like x.help.*', category=DeprecationWarning, module='IPython.*')
-else :
-    warnings.warn('iptest has been filtering out for Traitlets warnings messages, for 2 minor versions (since 4.x), please consider updating to use new API')
-
 if version_info < (6,):
     # nose.tools renames all things from `camelCase` to `snake_case` which raise an
     # warning with the runner they also import from standard import library. (as of Dec 2015)