tests/test-586

Improvement to 14ce129cfcd: Use try/except and pass filename on errors

Without the second part, the error message would be
  abort: Is a directory
instead of
  abort: Is a directory: /home/user/.cvspass

#!/bin/sh
# a test for issue586

hg init a
cd a
echo a > a
hg ci -Ama

hg init ../b
cd ../b
echo b > b
hg ci -Amb

hg pull -f ../a
hg merge
hg rm -f a
hg ci -Amc

hg st -A