uncaughtException when clients send non-trimmed headers

[randunel]

None of the error handlers are triggered when proxying client requests with non-trimmed headers.

I think the request shouldn't fail at all, but it's not up to http-proxy how node.js sanitizes the outgoing requests. At least an error that can be caught should be emitted, instead of terminating the process. Alternatively, http-proxy can sanitize the headers itself (see #997).

_http_outgoing.js:339
    throw new TypeError(
    ^

TypeError: Header name must be a valid HTTP Token ["cached-id "]
    at ServerResponse.OutgoingMessage.setHeader (_http_outgoing.js:339:11)
    at /.../node_modules/http-proxy/lib/http-proxy/passes/web-o
utgoing.js:86:13
    at Array.forEach (native)
    at Array.writeHeaders (/.../node_modules/http-proxy/lib/htt
p-proxy/passes/web-outgoing.js:84:35)
    at ClientRequest.<anonymous> (/.../node_modules/http-proxy/
lib/http-proxy/passes/web-incoming.js:150:20)
    at emitOne (events.js:90:13)
    at ClientRequest.emit (events.js:182:7)
    at HTTPParser.parserOnIncomingClient [as onIncoming] (_http_client.js:469:21)
    at HTTPParser.parserOnHeadersComplete (_http_common.js:103:23)
    at Socket.socketOnData (_http_client.js:359:20)
    at emitOne (events.js:90:13)
    at Socket.emit (events.js:182:7)
    at readableAddChunk (_stream_readable.js:153:18)
    at Socket.Readable.push (_stream_readable.js:111:10)
    at TCP.onread (net.js:529:20)