suggest a reason if we get no server response

modules/exploits/windows/smb/ms17_010_eternalblue.rb

@@ -277,20 +277,16 @@ class MetasploitModule < Msf::Exploit::Remote
   end
 
   def verify_arch
-    ret = false
-
     return true unless datastore['VerifyArch']
 
     # XXX: This sends a new DCE/RPC packet
     arch = dcerpc_getarch
 
-    if arch && arch == target_arch.first
-      ret = true
-    else
-      print_warning("Target arch is #{target_arch.first}, but server returned #{arch.inspect}")
-    end
+    return true if arch && arch == target_arch.first
 
-    ret
+    print_warning("Target arch is #{target_arch.first}, but server returned #{arch.inspect}")
+    print_warning("The DCE/RPC service or probe may be blocked") if arch.nil?
+    false
   end
 
   def print_core_buffer(os)