Catch both IOError and OSError, fix regression introduced by
8046f0a070a6
% qimport non-existing-file
abort: unable to read non-existing-file
% import URL
adding url.diff to series file
url.diff
% import patch that already exists
abort: patch "url.diff" already exists
applying url.diff
Now at: url.diff
foo
Patch queue now empty
% qimport -f
adding url.diff to series file
applying url.diff
Now at: url.diff
foo2
Patch queue now empty
% build diff with CRLF
adding b
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
% qimport CRLF diff
adding b.diff to series file
applying b.diff
Now at: b.diff