TYPO3 Core

I get an error message when I want to install a suggested extension of 'cal'.

Extensions suggested by extension "cal"
Extension "partner" was not available in the system. You may want to import it from the TYPO3 Extension Repository.

results in:
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Warning: array_keys(): The first argument should be an array in /var/www/vhosts/story-castle.net/httpdocs/typo3_src-4.1beta1a/typo3/mod/tools/em/class.em_index.php on line 1675

Warning: end(): Passed variable is not an array or object in /var/www/vhosts/story-castle.net/httpdocs/typo3_src-4.1beta1a/typo3/mod/tools/em/class.em_index.php on line 1676
Extension Manager
Extension import results
Error: The datatransfer did not succeed. The T3X file could not be fetched. Possible reasons: network problems, allow_url_fopen is off, curl is not enabled in Install tool.

(issue imported from #M4565)