test: update expected message

Curl 7.86 introduced a commit 5e259d7b ("pingpong: extend the response
reading error with errno") that breaks a test. Commit extended the
response reading error with errno.

Patch updates a message and fixes the test.

Part of #70
Follows up curl/curl#9443

Author: ligurio

test/smtp.test.lua

@@ -268,7 +268,11 @@ test:test("smtp.client", function(test)
     r = client:request(addr, '[email protected]',
                        '[email protected]',
                        'mail.body')
-    test:is(r.reason, 'response reading failed', 'unexpected response code')
+    local expected_reason = 'response reading failed'
+    if is_curl_version_ge(7, 86, 0) == true then
+        expected_reason = 'response reading failed (errno: 115)'
+    end
+    test:is(r.reason, expected_reason, 'unexpected response code')
     test:is(r.status, -1, 'expected code')
 
     r = client:request(addr, '[email protected]',
@@ -292,7 +296,11 @@ test:test("smtp.client", function(test)
     r = client:request(addr, '[email protected]',
                        '[email protected]',
                        'mail.body')
-    test:is(r.reason, 'response reading failed', 'unexpected response code')
+    local expected_reason = 'response reading failed'
+    if is_curl_version_ge(7, 86, 0) == true then
+        expected_reason = 'response reading failed (errno: 115)'
+    end
+    test:is(r.reason, expected_reason, 'unexpected response code')
     test:is(r.status, -1, 'expected code')
 
 end)