[web] fix os.rename usage on windows when destination exists os.rename on windows will raise OSError (or WindowsError subclass) when if destination file already exists. Also check that exception is EEXIST. There is an attempt to fix in f6ba947c but using IOError instead of OSError. Closes #14214794

^build$
^dist$
\.egg-info$
^.tox$
^.cache$
\.pyc$
\.pyo$
\.bak$
\.old$
\~$
\#.*?\#$
\.swp$
^doc/book/en/apidoc$
\.old$
syntax: regexp
.*/data.*/database/.*
.*/data/ldapdb/.*
.*/data/uicache/
.*/data/cubes/.*/i18n/.*\.po
^doc/html/
^doc/doctrees/
^doc/book/en/devweb/js_api/
^doc/_build
^doc/js_api/