fix backtrace printed when cannot get lock.
change lock error handling code so exceptions have useful info and
exception handling in one place.
add test case for when cannot get lock.
#!/usr/bin/env python
import sys
from mercurial import bdiff, mpatch
def test1(a, b):
d = bdiff.bdiff(a, b)
c = a
if d:
c = mpatch.patches(a, [d])
if c != b:
print "***", `a`, `b`
print "bad:"
print `c`[:200]
print `d`
def test(a, b):
print "***", `a`, `b`
test1(a, b)
test1(b, a)
test("a\nc\n\n\n\n", "a\nb\n\n\n")
test("a\nb\nc\n", "a\nc\n")
test("", "")
test("a\nb\nc", "a\nb\nc")
test("a\nb\nc\nd\n", "a\nd\n")
test("a\nb\nc\nd\n", "a\nc\ne\n")
test("a\nb\nc\n", "a\nc\n")
test("a\n", "c\na\nb\n")
test("a\n", "")
test("a\n", "b\nc\n")
test("a\n", "c\na\n")
test("", "adjfkjdjksdhfksj")
test("", "ab")
test("", "abc")
test("a", "a")
test("ab", "ab")
test("abc", "abc")
test("a\n", "a\n")
test("a\nb", "a\nb")
print "done"