make sure that the tests are actually executed in tox with Python 2.7

setup.py

@@ -836,6 +836,9 @@ def use_educated_guess(self):
     },
 )
 
+if sys.version_info <= (2, 7):
+    options["requires"] = options.pop("install_requires")
+
 if sys.version_info > (3, 0):
     options["use_2to3"] = True
 

src/_igraph/attributes.c

@@ -87,8 +87,11 @@ int igraphmodule_i_attribute_struct_index_vertex_names(
         PyErr_Format(
           PyExc_RuntimeError,
           "error while indexing vertex names; did you accidentally try to "
-          "use a non-hashable object as a vertex name earlier? "
-          "Check the name of vertex %R (%R)", value, key
+          "use a non-hashable object as a vertex name earlier?"
+#ifdef IGRAPH_PYTHON3
+          /* %R is not supported in Python 2.x */
+          " Check the name of vertex %R (%R)", value, key
+#endif
         );
       }
 

tests/test_attributes.py

@@ -1,4 +1,5 @@
 # vim:ts=4 sw=4 sts=4:
+import sys
 import unittest
 from igraph import *
 
@@ -102,7 +103,8 @@ def testUnhashableVertexNames(self):
 
         # Check the exception
         self.assertTrue(isinstance(err, RuntimeError))
-        self.assertTrue(repr(value) in str(err))
+        if sys.version_info >= (3, 4):
+            self.assertTrue(repr(value) in str(err))
 
     def testVertexNameIndexingBug196(self):
         g = Graph()

tests/test_foreign.py

@@ -226,7 +226,7 @@ def testPickle(self):
             pickle = bytes(pickle)
         else:
             pickle = "".join(map(chr, pickle))
-        with temporary_file(pickle, "wb") as tmpfname:
+        with temporary_file(pickle, "wb", binary=True) as tmpfname:
             g = Graph.Read_Pickle(pickle)
             self.assertTrue(isinstance(g, Graph))
             self.assertTrue(g.vcount() == 3 and g.ecount() == 1 and

tests/utils.py

@@ -47,7 +47,7 @@ def skipIf(condition, reason):
 
 
 @contextmanager
-def temporary_file(content=None, mode=None):
+def temporary_file(content=None, mode=None, binary=False):
     tmpf, tmpfname = tempfile.mkstemp()
     os.close(tmpf)
 
@@ -59,7 +59,7 @@ def temporary_file(content=None, mode=None):
 
     tmpf = open(tmpfname, mode)
     if content is not None:
-        if hasattr(content, "encode"):
+        if hasattr(content, "encode") and not binary:
             tmpf.write(dedent(content).encode("utf8"))
         else:
             tmpf.write(content)

tox.ini

@@ -14,6 +14,9 @@ deps =
 setenv =
     TESTING_IN_TOX=1
 
+[testenv:py27]
+commands = python -m unittest discover
+
 [flake8]
 max-line-length = 80
 select = C,E,F,W,B,B950