httppeer: wrap HTTPResponse.read() globally There were a handful of places in the code where HTTPResponse.read() was called with no explicit error handling or with inconsistent error handling. In order to eliminate this class of bug, we globally swap out HTTPResponse.read() with a unified error handler. I initially attempted to fix all call sites. However, after going down that rabbit hole, I figured it was best to just change read() to do what we want. This appears to be a worthwhile change, as the tests demonstrate many of our uncaught exceptions go away. To better represent this class of failure, we introduce a new error type. The main benefit over IOError is it can hold a hint. I'm receptive to tweaking its name or inheritance.

--- a/mercurial/error.py	Thu Apr 13 22:19:28 2017 -0700
+++ b/mercurial/error.py	Fri Apr 14 00:33:56 2017 -0700
@@ -252,3 +252,6 @@
 
 class CorruptedState(Exception):
     """error raised when a command is not able to read its state from file"""
+
+class RichIOError(Abort):
+    """An IOError that can also have a hint attached."""