Less wrapping of network errors

I don't think it's useful to wrap network errors like this, but I might
be missing something. I believe they tend to hide errors from the users.
If something in particular should be better worded, I believe the
builtin exception should be changed instead.

lib/rubygems/remote_fetcher.rb

@@ -51,6 +51,7 @@ def to_s # :nodoc:
 
   class UnknownHostError < FetchError
   end
+  deprecate_constant(:UnknownHostError)
 
   @fetcher = nil
 
@@ -262,15 +263,9 @@ def fetch_path(uri, mtime = nil, head = false)
     end
 
     data
-  rescue Timeout::Error
-    raise UnknownHostError.new('timed out', uri)
-  rescue IOError, SocketError, SystemCallError,
+  rescue Timeout::Error, IOError, SocketError, SystemCallError,
          *(OpenSSL::SSL::SSLError if Gem::HAVE_OPENSSL) => e
-    if e.message =~ /getaddrinfo/
-      raise UnknownHostError.new('no such name', uri)
-    else
-      raise FetchError.new("#{e.class}: #{e}", uri)
-    end
+    raise FetchError.new("#{e.class}: #{e}", uri)
   end
 
   def fetch_s3(uri, mtime = nil, head = false)

test/rubygems/test_gem_remote_fetcher.rb

@@ -496,6 +496,44 @@ def fetcher.fetch_http(uri, mtime = nil, head = nil)
     assert_equal url, e.uri
   end
 
+  def test_fetch_path_timeout_error
+    fetcher = Gem::RemoteFetcher.new nil
+    @fetcher = fetcher
+
+    def fetcher.fetch_http(uri, mtime = nil, head = nil)
+      raise Timeout::Error, 'timed out'
+    end
+
+    url = 'http://example.com/uri'
+
+    e = assert_raises Gem::RemoteFetcher::FetchError do
+      fetcher.fetch_path url
+    end
+
+    assert_match %r{Timeout::Error: timed out \(#{Regexp.escape url}\)\z},
+                 e.message
+    assert_equal url, e.uri
+  end
+
+  def test_fetch_path_getaddrinfo_error
+    fetcher = Gem::RemoteFetcher.new nil
+    @fetcher = fetcher
+
+    def fetcher.fetch_http(uri, mtime = nil, head = nil)
+      raise SocketError, 'getaddrinfo: nodename nor servname provided'
+    end
+
+    url = 'http://example.com/uri'
+
+    e = assert_raises Gem::RemoteFetcher::FetchError do
+      fetcher.fetch_path url
+    end
+
+    assert_match %r{SocketError: getaddrinfo: nodename nor servname provided \(#{Regexp.escape url}\)\z},
+                 e.message
+    assert_equal url, e.uri
+  end
+
   def test_fetch_path_openssl_ssl_sslerror
     fetcher = Gem::RemoteFetcher.new nil
     @fetcher = fetcher