Raise the error text of several connection attepts

in case of several hosts and async API.

This is what libpq does in sync API as well.

lib/pg/connection.rb

@@ -680,7 +680,7 @@ module Pollable
 				host_count = conninfo_hash[:host].to_s.count(",") + 1
 				stop_time = timeo * host_count + Process.clock_gettime(Process::CLOCK_MONOTONIC)
 			end
-			connection_attempts = 1
+			connection_errors = []
 
 			poll_status = PG::PGRES_POLLING_WRITING
 			until poll_status == PG::PGRES_POLLING_OK ||
@@ -721,12 +721,12 @@ module Pollable
 					else
 						connhost = "at \"#{host}\", port #{port}"
 					end
-					if connection_attempts < host_count.to_i
-						connection_attempts += 1
+					connection_errors << "connection to server #{connhost} failed: timeout expired"
+					if connection_errors.count < host_count.to_i
 						new_conninfo_hash = rotate_hosts(conninfo_hash.compact)
 						send(:reset_start2, self.class.send(:parse_connect_args, new_conninfo_hash))
 					else
-						raise PG::ConnectionBad.new("connection to server #{connhost} failed: timeout expired", connection: self)
+						raise PG::ConnectionBad.new(connection_errors.join("\n"), connection: self)
 					end
 				end
 

spec/pg/connection_spec.rb

@@ -369,25 +369,25 @@
 		end
 	end
 
-	it "times out after connect_timeout seconds" do
+	it "times out after 2 * connect_timeout seconds on two connections" do
 		TCPServer.open( 'localhost', 54320 ) do |serv|
 			start_time = Time.now
 			expect {
 				described_class.connect(
-					host: 'localhost',
+					host: 'localhost,localhost',
 					port: 54320,
 					connect_timeout: 1,
 					dbname: "test")
 			}.to raise_error do |error|
 				expect( error ).to be_an( PG::ConnectionBad )
-				expect( error.message ).to match( /timeout expired/ )
+				expect( error.message ).to match( /timeout expired.*timeout expired/m )
 				if PG.library_version >= 120000
-					expect( error.message ).to match( /\"localhost\"/ )
+					expect( error.message ).to match( /\"localhost\".*\"localhost\"/m )
 					expect( error.message ).to match( /port 54320/ )
 				end
 			end
 
-			expect( Time.now - start_time ).to be_between(0.9, 10).inclusive
+			expect( Time.now - start_time ).to be_between(1.9, 10).inclusive
 		end
 	end