Handle ConnectionReset+ConnectionAbort at any time (#168)

Previously we had a special case for BadStatusRead that would happen
only when we got a ConnectionAborted error reading the status line.
However, sometimes we get ConnectionReset instead. Also the HTTP
spec says that idempotent requests may be retried anytime a connection
is closed prematurely.

The change treats as retryable any ConnectionAborted OR ConnectionReset
error while reading the status line and headers. It removes the special
case BadStatusRead error.

Fixes #165 (I think).

src/error.rs

@@ -1,5 +1,5 @@
 use std::fmt;
-use std::io;
+use std::io::{self, ErrorKind};
 
 /// Errors that are translated to ["synthetic" responses](struct.Response.html#method.synthetic).
 #[derive(Debug)]
@@ -14,9 +14,6 @@ pub enum Error {
     ConnectionFailed(String),
     /// Too many redirects. Synthetic error `500`.
     TooManyRedirects,
-    /// We fail to read the status line. This happens for pooled connections when
-    /// TLS fails and we don't notice until trying to read.
-    BadStatusRead,
     /// A status line we don't understand `HTTP/1.1 200 OK`. Synthetic error `500`.
     BadStatus,
     /// A header line that couldn't be parsed. Synthetic error `500`.
@@ -37,11 +34,11 @@ pub enum Error {
 }
 
 impl Error {
-    // If the error is bad status read, which might happen if a TLS connections is
-    // closed and we only discover it when trying to read the status line from it.
-    pub(crate) fn is_bad_status_read(&self) -> bool {
+    // Return true iff the error was due to a connection closing.
+    pub(crate) fn connection_closed(&self) -> bool {
         match self {
-            Error::BadStatusRead => true,
+            Error::Io(e) if e.kind() == ErrorKind::ConnectionAborted => true,
+            Error::Io(e) if e.kind() == ErrorKind::ConnectionReset => true,
             _ => false,
         }
     }
@@ -54,7 +51,6 @@ impl Error {
             Error::DnsFailed(_) => 400,
             Error::ConnectionFailed(_) => 500,
             Error::TooManyRedirects => 500,
-            Error::BadStatusRead => 500,
             Error::BadStatus => 500,
             Error::BadHeader => 500,
             Error::Io(_) => 500,
@@ -75,7 +71,6 @@ impl Error {
             Error::DnsFailed(_) => "Dns Failed",
             Error::ConnectionFailed(_) => "Connection Failed",
             Error::TooManyRedirects => "Too Many Redirects",
-            Error::BadStatusRead => "Failed to read status line",
             Error::BadStatus => "Bad Status",
             Error::BadHeader => "Bad Header",
             Error::Io(_) => "Network Error",
@@ -96,7 +91,6 @@ impl Error {
             Error::DnsFailed(err) => format!("Dns Failed: {}", err),
             Error::ConnectionFailed(err) => format!("Connection Failed: {}", err),
             Error::TooManyRedirects => "Too Many Redirects".to_string(),
-            Error::BadStatusRead => "Failed to read status line".to_string(),
             Error::BadStatus => "Bad Status".to_string(),
             Error::BadHeader => "Bad Header".to_string(),
             Error::Io(ioe) => format!("Network Error: {}", ioe),