diff --git a/test/test_certutils.py b/test/test_certutils.py
index 95a7280ef..55fcc1dc4 100644
--- a/test/test_certutils.py
+++ b/test/test_certutils.py
@@ -116,11 +116,15 @@ class TestDummyCert:
 
 class TestSSLCert:
     def test_simple(self):
-        c = certutils.SSLCert.from_pem(file(tutils.test_data.path("data/text_cert"), "rb").read())
+        with open(tutils.test_data.path("data/text_cert"), "rb") as f:
+            d = f.read()
+        c = certutils.SSLCert.from_pem(d)
         assert c.cn == "google.com"
         assert len(c.altnames) == 436
 
-        c = certutils.SSLCert.from_pem(file(tutils.test_data.path("data/text_cert_2"), "rb").read())
+        with open(tutils.test_data.path("data/text_cert_2"), "rb") as f:
+            d = f.read()
+        c = certutils.SSLCert.from_pem(d)
         assert c.cn == "www.inode.co.nz"
         assert len(c.altnames) == 2
         assert c.digest("sha1")
@@ -134,12 +138,15 @@ class TestSSLCert:
         c.has_expired
 
     def test_err_broken_sans(self):
-        c = certutils.SSLCert.from_pem(file(tutils.test_data.path("data/text_cert_weird1"), "rb").read())
+        with open(tutils.test_data.path("data/text_cert_weird1"), "rb") as f:
+            d = f.read()
+        c = certutils.SSLCert.from_pem(d)
         # This breaks unless we ignore a decoding error.
         c.altnames
 
     def test_der(self):
-        d = file(tutils.test_data.path("data/dercert"),"rb").read()
+        with open(tutils.test_data.path("data/dercert"), "rb") as f:
+            d = f.read()
         s = certutils.SSLCert.from_der(d)
         assert s.cn