Problem: pypa moved get-pip again

Solution: use new advised URLs

dev.py

@@ -53,11 +53,11 @@ def install_pip():
     try:
         get_pip = os.path.join(tmp, 'get-pip.py')
         if sys.version_info < (3, ):
-            GET_PIP_URL = 'https://bootstrap.pypa.io/2.7/get-pip.py'
+            GET_PIP_URL = 'https://bootstrap.pypa.io/pip/2.7/get-pip.py'
         elif (sys.version_info.major, sys.version_info.minor) == (3, 5):
-            GET_PIP_URL = 'https://bootstrap.pypa.io/3.5/get-pip.py'
+            GET_PIP_URL = 'https://bootstrap.pypa.io/pip/3.5/get-pip.py'
         else:
-            GET_PIP_URL = 'https://bootstrap.pypa.io/get-pip.py'
+            GET_PIP_URL = 'https://bootstrap.pypa.io/pip/get-pip.py'
         with open(get_pip, 'wb') as f:
             f.write(urlopen(GET_PIP_URL).read())