url: fix UnicodeDecodeError on certificate verification error
SSLSocket.getpeercert() returns tuple containing unicode for 'subject'.
Since Mercurial does't support IDN at all, it just returns error for non-ascii
certname.
test that 'hg commit' does not crash if the user removes a newly added file
$ hg init
$ echo This is file a1 > a
$ hg add a
$ hg commit -m "commit #0"
$ touch b
$ hg add b
$ rm b
$ hg commit -A -m"comment #1"
removing b
nothing changed
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