Turn off pex warnings for Pants when run from a pex.

src/python/pants/bin/pants_loader.py

@@ -43,6 +43,11 @@ def setup_warnings():
     # However, we do turn off deprecation warnings for libraries that Pants uses for which we do not have a fixed
     # upstream version, typically because the library is no longer maintained.
     warnings.simplefilter('default', category=DeprecationWarning)
+
+    # If we're running from a pex, suppress pex warnings about transitive dependencies that do not
+    # properly declare dependencies on setuptools to support their namespace packages.
+    warnings.filterwarnings('ignore', category=UserWarning, module='pex')
+
     # TODO: Future has a pending PR to fix deprecation warnings at https://github.com/PythonCharmers/python-future/pull/421.
     # Remove this filter once that gets merged.
     warnings.filterwarnings('ignore', category=DeprecationWarning, module="future")