suppress warnings in ipexec tests

shim imports cause lots of warnings

should we always suppress warnings in these tests?

IPython/testing/tools.py

@@ -217,7 +217,10 b' def ipexec(fname, options=None, commands=()):'
     full_fname = os.path.join(test_dir, fname)
     full_cmd = ipython_cmd + cmdargs + [full_fname]
     env = os.environ.copy()
-    env.pop('PYTHONWARNINGS', None)  # Avoid extraneous warnings appearing on stderr
+    # FIXME: ignore all warnings in ipexec while we have shims
+    # should we keep suppressing warnings here, even after removing shims?
+    env['PYTHONWARNINGS'] = 'ignore'
+    # env.pop('PYTHONWARNINGS', None)  # Avoid extraneous warnings appearing on stderr
     for k, v in env.items():
         # Debug a bizarre failure we've seen on Windows:
         # TypeError: environment can only contain strings