Correct the oldest requirements environment (#6569)

I observed that the current set of oldest requirements do not correspond to any environment, except the specific Xenial image in Travis CI (and standard Xenial containers will also fail).

It is because the requirements make cryptography and requests fail against standard libraries available in the typical Linux distributions that are targeted by the oldest requirements approach (Centos 6, Centos 7, Xenial, Jessie).

This PR fixes that, by aligning the minimal version requirements of cryptography and requests to the maximal versions that are available on Centos 6. Centos 7, Jessie and Xenial stay unusable with oldest requirements for other reasons, but at least one old and supported Linux distribution is able to run the tests with oldest requirements out of the box.

A test is also corrected to match the expected error message that old versions of urllib3 will raise.

acme/acme/client_test.py

@@ -707,6 +707,7 @@ class ClientTest(ClientTestBase):
             self.certr,
             self.rsn)
 
+
 class ClientV2Test(ClientTestBase):
     """Tests for acme.client.ClientV2."""
 
@@ -950,7 +951,6 @@ class ClientNetworkTest(unittest.TestCase):
         self.assertEqual(jws.signature.combined.kid, u'acct-uri')
         self.assertEqual(jws.signature.combined.url, u'url')
 
-
     def test_check_response_not_ok_jobj_no_error(self):
         self.response.ok = False
         self.response.json.return_value = {}
@@ -1113,8 +1113,8 @@ class ClientNetworkTest(unittest.TestCase):
 
         # Requests Library Exceptions
         except requests.exceptions.ConnectionError as z: #pragma: no cover
-            self.assertTrue("('Connection aborted.', error(111, 'Connection refused'))"
-                              == str(z) or "[WinError 10061]" in str(z))
+            self.assertTrue("'Connection aborted.'" in str(z) or "[WinError 10061]" in str(z))
+
 
 class ClientNetworkWithMockedResponseTest(unittest.TestCase):
     """Tests for acme.client.ClientNetwork which mock out response."""

acme/setup.py

@@ -9,15 +9,15 @@ version = '0.31.0.dev0'
 install_requires = [
     # load_pem_private/public_key (>=0.6)
     # rsa_recover_prime_factors (>=0.8)
-    'cryptography>=0.8',
+    'cryptography>=1.2.3',
     # formerly known as acme.jose:
     'josepy>=1.0.0',
     # Connection.set_tlsext_host_name (>=0.13)
     'mock',
-    'PyOpenSSL>=0.13',
+    'PyOpenSSL>=0.13.1',
     'pyrfc3339',
     'pytz',
-    'requests[security]>=2.4.1',  # security extras added in 2.4.1
+    'requests[security]>=2.6.0',  # security extras added in 2.4.1
     'requests-toolbelt>=0.3.0',
     'setuptools',
     'six>=1.9.0',  # needed for python_2_unicode_compatible

setup.py

@@ -37,7 +37,7 @@ install_requires = [
     # in which we added 2.6 support (see #2243), so we relax the requirement.
     'ConfigArgParse>=0.9.3',
     'configobj',
-    'cryptography>=1.2',  # load_pem_x509_certificate
+    'cryptography>=1.2.3',  # load_pem_x509_certificate
     'josepy',
     'mock',
     'parsedatetime>=1.3',  # Calendar.parseDT

tools/oldest_constraints.txt

@@ -37,13 +37,13 @@ pytz==2012rc0
 
 # Our setup.py constraints
 cloudflare==1.5.1
-cryptography==1.2.0
+cryptography==1.2.3
 google-api-python-client==1.5
 oauth2client==2.0
 parsedatetime==1.3
 pyparsing==1.5.5
 python-digitalocean==1.11
-requests[security]==2.4.1
+requests[security]==2.6.0
 
 # Ubuntu Xenial constraints
 ConfigArgParse==0.10.0