Python changed traceback output a bit:

- added '^^^^^^^' and '~~^~~'
- changed lineno of frame corresponding to __exit__ to be at line of `with ...`

-> Adjust to that by introducing a bit more generalized conditionals in
   assertDoc.

Here is, for example, how test_defer_excchain_traceback was failing on py3.11:

E           Failed: not equal:
E           Differences (unified diff with -expected +actual):
E               @@ -1,6 +1,7 @@
E                Traceback (most recent call last):
E               -  File "PYGOLANG/golang/__init__.py", line ..., in _
E               +  File "PYGOLANG/golang/__init__.py", line 103, in _
E                    return f(*argv, **kw)
E               -  File "PYGOLANG/golang/golang_test.py", line ..., in caller
E               +           ^^^^^^^^^^^^^^
E               +  File "PYGOLANG/golang/golang_test.py", line 1550, in caller
E                    raise RuntimeError("ccc")
E                RuntimeError: ccc
E               @@ -9,7 +10,7 @@
E                <BLANKLINE>
E                Traceback (most recent call last):
E               -  File "PYGOLANG/golang/__init__.py", line ..., in __exit__
E               +  File "PYGOLANG/golang/__init__.py", line 180, in __exit__
E                    d()
E               -  File "PYGOLANG/golang/golang_test.py", line ..., in q2
E               +  File "PYGOLANG/golang/golang_test.py", line 1548, in q2
E                    raise RuntimeError("bbb")
E                RuntimeError: bbb
E               @@ -18,14 +19,16 @@
E                <BLANKLINE>
E                Traceback (most recent call last):
E               -  File "PYGOLANG/golang/golang_test.py", line ..., in test_defer_excchain_traceback
E               +  File "PYGOLANG/golang/golang_test.py", line 1553, in test_defer_excchain_traceback
E                    caller()
E               -  ...
E               -  File "PYGOLANG/golang/__init__.py", line ..., in _
E               -    return f(*argv, **kw)
E               -  File "PYGOLANG/golang/__init__.py", line ..., in __exit__
E               +  File "/home/kirr/src/tools/go/py3.venv/lib/python3.11/site-packages/decorator.py", line 232, in fun
E               +    return caller(func, *(extras + args), **kw)
E               +           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
E               +  File "PYGOLANG/golang/__init__.py", line 102, in _
E               +    with __goframe__:
E               +  File "PYGOLANG/golang/__init__.py", line 179, in __exit__
E               +    with __goframe__:
E               +  File "PYGOLANG/golang/__init__.py", line 180, in __exit__
E                    d()
E               -  File "PYGOLANG/golang/__init__.py", line ..., in __exit__
E               -    d()
E               -  File "PYGOLANG/golang/golang_test.py", line ..., in q1
E               +  File "PYGOLANG/golang/golang_test.py", line 1545, in q1
E                    raise RuntimeError("aaa")
E                RuntimeError: aaa