Clarify location of certain invalid docstrings.

[anntzer]

Closes #115 Closes #123

If one adds the following invalid docstring at the end of
doc/example.py

def bar():
    """
    Parameters
    ----------
    a : int

    Parameters
    ----------
    b : float
    """

then as of numpydoc master the error message is

ValueError: The section Parameters appears twice in the docstring of None in None.

This patch fixes the error message to give

ValueError: The section Parameters appears twice in the docstring of <function bar at 0x7fa5c9d20e18> in /path/to/numpydoc/doc/example.py.

Initially noticed at matplotlib/matplotlib#11859 (comment).

[jnothman]

Does this fix #115? Is it superseding #123 Sorry I'm not investigating now

[anntzer]

I think that it does fix #115 (well, there isn't a minimum repro for it but looks likely the same) which I didn't notice, and does so more simply than #123 by reusing the get_doc_info logic rather than reimplementing it all.

[jnothman]

I agree it is simpler. Is it reasonable to add a test?

[anntzer]

It's not so easy. I wrote

diff --git i/numpydoc/tests/test_main.py w/numpydoc/tests/test_main.py
index e565bb2..e0b1fb3 100644
--- i/numpydoc/tests/test_main.py
+++ w/numpydoc/tests/test_main.py
@@ -4,12 +4,14 @@ from contextlib import contextmanager
 import os
 import sys
 import tempfile
+import warnings
 try:
     from StringIO import StringIO
 except ImportError:
     from io import StringIO
 
 from numpydoc.__main__ import main
+import pytest
 
 
 PACKAGE_CODE = """
@@ -29,6 +31,17 @@ def foo(a, b=5):
     something_else
         bar
     '''
+
+def oops():
+    '''
+    Parameters
+    ----------
+    a : int
+
+    Parameters
+    ----------
+    b : float
+    '''
 """
 
 
@@ -72,6 +85,9 @@ def test_main():
     with _mock_module('somepackage1'):
         out = _capture_main('somepackage1.module.foo')
     assert out.startswith('Hello world\n')
+    with pytest.raises(ValueError, match='docstring of <function oops'):
+        with _mock_module('somepackage1'):
+            out = _capture_main('somepackage1.module.oops')
     with _mock_module('somepackage2'):
         out = _capture_main('somepackage2.module')
     assert out.startswith('This module has test')

which should have been a proper test, but that also works as of master because that tests numpydoc.main, which already uses get_doc_object; what really needs to be tested is that numpydoc.numpydoc.mangle_signature also uses get_doc_object but there's no test for mangle_signature at all right now (as noted by the comment "# TODO: does not currently check that numpydoc transformations are applied").