gdb/python: reformat an error string

gdb/python: reformat an error string

While working on another patch I noticed an oddly formatted error
message in the Python code.

When 'set python print-stack message' is in effect then consider this
Python script:

  class TestCommand (gdb.Command):
      def __init__ (self):
          gdb.Command.__init__ (self, "test-cmd", gdb.COMMAND_DATA)
      def invoke(self, args, from_tty):
          raise RuntimeError ("bad")
  TestCommand ()

And this GDB session:

  (gdb) source path/to/python/script.py
  (gdb) test-cmd
  Python Exception <class 'RuntimeError'> bad:
  Error occurred in Python: bad

The line 'Python Exception <class 'RuntimeError'> bad:' doesn't look
terrible in this situation, the colon at the end of the first line
makes sense given the second line.

However, there are places in GDB where there is no second line
printed, for example consider this python script:

  def stop_listener (e):
      raise RuntimeError ("bad")
  gdb.events.stop.connect (stop_listener)

Then this GDB session:

  (gdb) file helloworld.exe
  (gdb) start
  Temporary breakpoint 1 at 0x40112a: file hello.c, line 6.
  Starting program: helloworld.exe

  Temporary breakpoint 1, main () at hello.c:6
  6	  printf ("Hello World\n");
  Python Exception <class 'RuntimeError'> bad:
  (gdb) si
  0x000000000040112f	6	  printf ("Hello World\n");
  Python Exception <class 'RuntimeError'> bad:

In this case there is no auxiliary information displayed after the
warning, and the line ending in the colon looks weird to me.

A quick survey of the code seems to indicate that it is not uncommon
for there to be no auxiliary information line printed, its not just
the one case I found above.

I propose that the line that currently looks like this:

  Python Exception <class 'RuntimeError'> bad:

Be reformatted like this:

  Python Exception <class 'RuntimeError'>: bad

I think this looks fine then in either situation.  The first now looks
like this:

  (gdb) test-cmd
  Python Exception <class 'RuntimeError'>: bad
  Error occurred in Python: bad

And the second like this:

  (gdb) si
  0x000000000040112f	6	  printf ("Hello World\n");
  Python Exception <class 'RuntimeError'>: bad

There's just two tests that needed updating.  Errors are checked for
in many more tests, but most of the time the pattern doesn't care
about the colon.

gdb/ChangeLog:

	* python/python.c (gdbpy_print_stack): Reformat an error message.

gdb/testsuite/ChangeLog:

	* gdb.python/py-framefilter.exp: Update expected results.
	* gdb.python/python.exp: Update expected results.