More clear behavior when passing non-strings to note

[tybug]

Consider the following:

from hypothesis import *
from hypothesis.strategies import *

class A:
    pass

@given(builds(A))
def f(a):
    note(a)
    assert False

f()

This errors with the following traceback:

Traceback (most recent call last):
  File "/Users/tybug/Desktop/Liam/coding/sandbox/__hypothesis.py", line 12, in <module>
    f()
  File "/Users/tybug/Desktop/Liam/coding/sandbox/__hypothesis.py", line 8, in f
    def f(a):
              
  File "/Users/tybug/Desktop/Liam/coding/hypothesis/hypothesis-python/src/hypothesis/core.py", line 1599, in wrapped_test
    raise the_error_hypothesis_found
  File "/Users/tybug/Desktop/Liam/coding/hypothesis/hypothesis-python/src/hypothesis/core.py", line 1566, in wrapped_test
    state.run_engine()
  File "/Users/tybug/Desktop/Liam/coding/hypothesis/hypothesis-python/src/hypothesis/core.py", line 1214, in run_engine
    _raise_to_user(errors_to_report, self.settings, report_lines)
  File "/Users/tybug/Desktop/Liam/coding/hypothesis/hypothesis-python/src/hypothesis/core.py", line 1223, in _raise_to_user
    add_note(err, note)
  File "/Users/tybug/Desktop/Liam/coding/hypothesis/hypothesis-python/src/hypothesis/internal/compat.py", line 50, in add_note
    exc.add_note(note)
TypeError: note must be a str, not 'A'

In this case, it's relatively obvious that the note call is the culprit. But it may be more confusing in more complicated functions, since that information gets trimmed from the traceback.

I propose we either:

• fail early and explicitly when note is passed a non-str value
• automatically coerce note(x) to report(str(x)) instead of report(x)

This came up in practice in

hypothesis/hypothesis-python/tests/nocover/test_explore_arbitrary_languages.py

Lines 115 to 120 in 798803a

	try:
	runner.run()
	finally:
	if data is not None:
	note(root)
	assume(runner.interesting_examples)

(fix to come!)

[Zac-HD]

Let's use our pretty-printer for non-strings, to give a maximally-informative string form. Thanks for spotting this!