https://github.com/testing-cabal/testtools/commit/29004731f9c480b7c44a9c2605513d50d372898f.patch
Should be fixed in the next release

From 29004731f9c480b7c44a9c2605513d50d372898f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Miro=20Hron=C4=8Dok?= <miro@hroncok.cz>
Date: Thu, 17 May 2018 17:52:26 +0200
Subject: [PATCH] Fix the tests on Python 3.7

Exception's repr got changed not to include trailing comma

Fixes https://github.com/testing-cabal/testtools/issues/270
---
 .travis.yml                                |  1 +
 testtools/tests/matchers/test_exception.py | 11 +++++++++--
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/.travis.yml b/.travis.yml
index 7f1f4db7..784608e0 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -5,6 +5,7 @@ python:
   - "3.4"
   - "3.5"
   - "3.6"
+  - "3.7-dev"
   - "pypy"
 
 install:
diff --git a/testtools/tests/matchers/test_exception.py b/testtools/tests/matchers/test_exception.py
index 6cd80af1..acd39252 100644
--- a/testtools/tests/matchers/test_exception.py
+++ b/testtools/tests/matchers/test_exception.py
@@ -32,15 +32,22 @@ class TestMatchesExceptionInstanceInterface(TestCase, TestMatchersInterface):
     matches_matches = [error_foo]
     matches_mismatches = [error_bar, error_base_foo]
 
+    if sys.version_info >= (3, 7):
+        # exception's repr has changed
+        _e = ''
+    else:
+        _e = ','
+
     str_examples = [
-        ("MatchesException(Exception('foo',))",
+        ("MatchesException(Exception('foo'%s))" % _e,
          MatchesException(Exception('foo')))
         ]
     describe_examples = [
         ("%r is not a %r" % (Exception, ValueError),
          error_base_foo,
          MatchesException(ValueError("foo"))),
-        ("ValueError('bar',) has different arguments to ValueError('foo',).",
+        ("ValueError('bar'%s) has different arguments to ValueError('foo'%s)."
+         % (_e, _e),
          error_bar,
          MatchesException(ValueError("foo"))),
         ]
rch' size='10' name='q' value=''/>
<input type='submit' value='search'/>
</form>
</td></tr></table>
<div class='path'>path: <a href='/guix/log/?id=38fc0acf4d6752a8a3dcdab41eff1b0b5ed5e2d8'>root</a>/<a href='/guix/log/gnu?id=38fc0acf4d6752a8a3dcdab41eff1b0b5ed5e2d8'>gnu</a>/<a href='/guix/log/gnu/installer?id=38fc0acf4d6752a8a3dcdab41eff1b0b5ed5e2d8'>installer</a>/<a href='/guix/log/gnu/installer/newt?id=38fc0acf4d6752a8a3dcdab41eff1b0b5ed5e2d8'>newt</a>/<a href='/guix/log/gnu/installer/newt/network.scm?id=38fc0acf4d6752a8a3dcdab41eff1b0b5ed5e2d8'>network.scm</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/gnu/installer/newt/network.scm?id=38fc0acf4d6752a8a3dcdab41eff1b0b5ed5e2d8&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2022-10-17 16:34:07 +0400'>2022-10-17</span></td><td><a href='/guix/commit/gnu/installer/newt/network.scm?id=883fb8f41b08a8455f16c736a83fb1ae8a3df0a1'>installer: Factorize url-alive? in internet check.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/installer/newt/network.scm (wait-service-online): Factorize url-alive?
in internet check.
</span></span></td><td>Andrew Tropin</td></tr>
<tr><td><span title='2022-10-17 10:22:15 +0400'>2022-10-17</span></td><td><a href='/guix/commit/gnu/installer/newt/network.scm?id=094b357783ae92fc5652f8a8c61e0b96b342d09d'>installer: Relax internet check availability criteria.</a><span class='msg-avail'>...<span class='msg-tooltip'>Checks the availability of the mirror bordeaux.guix.gnu.org in addition to
ci.guix.gnu.org.  This allows to proceed the installation if the
ci.guix.gnu.org is unavailable.

* gnu/installer/newt/network.scm (wait-service-online): Relax internet check
availability criteria.

Signed-off-by: Andrew Tropin &lt;andrew@trop.in&gt;
</span></span></td><td>aleksandr barakin</td></tr>
<tr><td><span title='2022-02-02 16:46:44 +0100'>2022-02-02</span></td><td><a href='/guix/commit/gnu/installer/newt/network.scm?id=726d0bd2f36363392ba2fcefd6e5d4aeed27dc9e'>installer: Use named prompt to abort or break installer steps.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/installer/steps.scm (run-installer-steps): Set up
'installer-step prompt.
* gnu/installer/newt/ethernet.scm (run-ethernet-page)
* gnu/installer/newt/final.scm (run-config-display-page,
run-install-failed-page)
* gnu/installer/newt/keymap.scm (run-layout-page, run-variant-page)
* gnu/installer/newt/locale.scm (run-language-page,
run-territory-page, run-codeset-page, run-modifier-page,
run-locale-page)
* gnu/installer/newt/network.scm (run-technology-page,
wait-service-online)
* gnu/installer/newt/page.scm (run-listbox-selection-page,
run-checkbox-tree-page)
* gnu/installer/newt/partition.scm (button-exit-action)
* gnu/installer/newt/services.scm (run-desktop-environments-cbt-page,
run-networking-cbt-page, run-other-services-cbt-page,
run-network-management-page)
* gnu/installer/newt/timezone.scm (run-timezone-page)
* gnu/installer/newt/user.scm (run-user-page)
* gnu/installer/newt/welcome.scm (run-menu-page)
* gnu/installer/newt/wifi.scm (run-wifi-page): Use the 'installer-step
prompt to abort.

Signed-off-by: Mathieu Othacehe &lt;othacehe@gnu.org&gt;
</span></span></td><td>Josselin Poiret</td></tr>
<tr><td><span title='2022-01-14 14:29:08 +0100'>2022-01-14</span></td><td><a href='/guix/commit/gnu/installer/newt/network.scm?id=ee897e5f51104f41b3c2a0c2cbc7eb4e6c1e4d3e'>installer: Check if ci.guix.gnu.org can be reached.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/installer.scm (installer-program): Add gnutls extension.
* gnu/installer/newt/network.scm (wait-service-online): Check if the CI server
can be reached.
</span></span></td><td>Mathieu Othacehe</td></tr>