As you may know, Xoops uses templates created with Smarty. Templates can call other templates. For example a template "A" can, inside its code, call the template named "B" (with the Smarty instruction <{include file="db:xxx.html"}>) Then in the file named xoops_version.php, if the template A is described (with the lines begining with $modversion['templates'][1]['file']...) BEFORE the template B, then you can see this warning message. The module's designer should review the order of templates declarations.
Unable to read resource
If the error is during the installation process, then this is correct.
If this error is experienced when using the module, the module developer may have forgotten about putting the $modversion[...] definition of the template in the module's xoops_version.php