This patch fixes test failure related to reported source code locations.
It is a backport of this patch:

  commit 6a5f38b5ab12260fde8a0463acd433bc2d34dbcf
  Author: Louis Sautier <sautier.louis@gmail.com>
  Date:   Sat Oct 3 02:37:53 2020 +0200

      Fix tests with Python 3.9, closes #549 (#586)

      Stop allowing failures on Python nightly.

diff --git a/pyflakes/test/test_api.py b/pyflakes/test/test_api.py
index 128aa69..b728e65 100644
--- a/pyflakes/test/test_api.py
+++ b/pyflakes/test/test_api.py
@@ -515,6 +515,8 @@ def foo(bar=baz, bax):
             if ERROR_HAS_LAST_LINE:
                 if PYPY and sys.version_info >= (3,):
                     column = 7
+                elif sys.version_info >= (3, 9):
+                    column = 21
                 elif sys.version_info >= (3, 8):
                     column = 9
                 else:
@@ -543,6 +545,8 @@ foo(bar=baz, bax)
             if ERROR_HAS_LAST_LINE:
                 if PYPY and sys.version_info >= (3,):
                     column = 12
+                elif sys.version_info >= (3, 9):
+                    column = 17
                 elif sys.version_info >= (3, 8):
                     column = 14
                 else:
@@ -577,6 +581,8 @@ foo(bar=baz, bax)
                 position_end = 1
                 if PYPY:
                     column = 6
+                elif ver >= (3, 9):
+                    column = 13
                 else:
                     column = 7
                     # Column has been "fixed" since 3.2.4 and 3.3.1
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<tr><td><span title='2017-09-26 11:42:06 -0400'>2017-09-26</span></td><td><a href='/guix/commit/gnu/packages/libunwind.scm?id=373cda6ac6293d2aa5273ac28a505a2f0beb09dc'>gnu: libunwind: Update to 1.2.1.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/libunwind.scm (libunwind): Upate to 1.2.1.
[source]: Remove 'libunwind-CVE-2015-3239.patch'.
* gnu/packages/patches/libunwind-CVE-2015-3239.patch: Delete file.
* gnu/local.mk (dist_patch_DATA): Remove it.
</span></span></td><td>Leo Famulari</td></tr>