add util.py which is the home of wrap_errors helper now

gevent/util.py

+class wrap_errors(object):
+    """Helper to make function return an exception, rather than raise it.
+
+    Because every exception that is unhandled by greenlet will be logged by the hub,
+    it is desirable to prevent non-error exceptions from leaving a greenlet.
+    This can done with simple try/except construct:
+
+    def func1(*args, **kwargs):
+        try:
+            return func(*args, **kwargs)
+        except (A, B, C), ex:
+            return ex
+
+    wrap_errors provides a shortcut to write that in one line:
+
+    func1 = wrap_errors((A, B, C), func)
+
+    It also preserves __str__ and __repr__ of the original function.
+    """
+
+    def __init__(self, errors, func):
+        """Make a new function from `func', such that it catches `errors' (an
+        Exception subclass, or a tuple of Exception subclasses) and return
+        it as a value.
+        """
+        self.errors = errors
+        self.func = func
+
+    def __call__(self, *args, **kwargs):
+        try:
+            return self.func(*args, **kwargs)
+        except self.errors, ex:
+            return ex
+
+    def __str__(self):
+        return str(self.func)
+
+    def __repr__(self):
+        return repr(self.func)
+
+    def __getattr__(self, item):
+        return getattr(self.func, item)
+
+