further fix the build

requirements-to-freeze.txt

@@ -1,6 +1,7 @@
 pytest
 pytest-cov
 pytest-httpbin
+pytest-mock
 PySocks
 sphinx
 codecov

requirements.txt

@@ -6,17 +6,21 @@ coverage==4.3.4
 decorator==4.0.11
 docutils==0.13.1
 Flask==0.12
+funcsigs==1.0.2
 httpbin==0.5.0
 imagesize==0.7.1
 itsdangerous==0.24
 Jinja2==2.9.4
 MarkupSafe==0.23
+mock==2.0.0
+pbr==1.10.0
 py==1.4.32
 Pygments==2.1.3
 PySocks==1.6.5
 pytest==3.0.5
 pytest-cov==2.4.0
 pytest-httpbin==0.2.3
+pytest-mock==1.5.0
 pytz==2016.10
 requests==2.12.4
 six==1.10.0