WordPress: save `get_template_part()` to variable

This isn’t what get_template_part was for, get_template_part essentially behaves like PHP’s require function. Justin Tadlock writes a lot more about this here and also talks about a WordPress function that might be more useful to you – locate_template. Alternatively, if you did want to hack this functionality using get_template_part, you could use template buffering:

Difficulty updating WordPress from 3.9.1 to 4.0

You need to check your file/folder permissions. Your webhost may have them set too strictly for WordPress to write its own temp folders and extract its own archive in /wp-content/upgrade/. See Changing File Permissions « WordPress Codex: Typically, all files should be owned by your user (ftp) account on your web server, and should be writable by … Read more

Difficulty updating WordPress from 3.9.1 to 4.0

You need to check your file/folder permissions. Your webhost may have them set too strictly for WordPress to write its own temp folders and extract its own archive in /wp-content/upgrade/. See Changing File Permissions « WordPress Codex: Typically, all files should be owned by your user (ftp) account on your web server, and should be writable by … Read more