Allow to fetch from URLs that contain allowed reserved delimiters

Go has a bug where it does not include all allowed reserved sub-delimiters
As a workaround, a http.Get is extended to keep the paths un-escaped.

It is expected that URL are previously escaped, so there should be no 
negative side effect

For more information on bug: golang/go#5684

fetcher/http/client.go

@@ -0,0 +1,52 @@
+package http
+
+import (
+	"net/http"
+	"net/url"
+)
+
+// A Client extends http.Client and patches incorrect URL path escaping
+// for more information on bug: https://github.com/golang/go/issues/5684
+type Client struct {
+	http.Client
+}
+
+// Get issues a GET to the specified URL.  If the response is one of the
+// following redirect codes, Get follows the redirect after calling the
+// Client's CheckRedirect function.
+//
+//    301 (Moved Permanently)
+//    302 (Found)
+//    303 (See Other)
+//    307 (Temporary Redirect)
+//
+// An error is returned if the Client's CheckRedirect function fails
+// or if there was an HTTP protocol error. A non-2xx response doesn't
+// cause an error.
+//
+// When err is nil, resp always contains a non-nil resp.Body.
+// Caller should close resp.Body when done reading from it.
+//
+func (c *Client) Get(urlStr string) (resp *http.Response, err error) {
+	fu, err := url.Parse(urlStr)
+	if err != nil {
+		return nil, err
+	}
+	u := &url.URL{
+		Scheme: fu.Scheme,
+		Host:   fu.Host,
+		Opaque: fu.Path,
+	}
+
+	req := &http.Request{
+		Method:     "GET",
+		URL:        u,
+		Proto:      "HTTP/1.1",
+		ProtoMajor: 1,
+		ProtoMinor: 1,
+		Header:     make(http.Header),
+		Host:       u.Host,
+	}
+
+	return c.Do(req)
+}

fetcher/http/http.go

@@ -30,7 +30,7 @@ func (f *Fetcher) Fetch(url string, destination string) error {
 	if _, err := os.Stat(destination); os.IsNotExist(err) {
 		start := time.Now()
 
-		client := &http.Client{Transport: transport}
+		client := Client{http.Client{Transport: transport}}
 		resp, err := client.Get(url)
 
 		if err != nil {