Attempt to disable pip's annoying warning about Python 2.

It looks like that got interpreted as an error?
https://ci.appveyor.com/project/denik/gevent/builds/32221986/job/2hveawuceoxsbdxj

.travis.yml

@@ -19,6 +19,9 @@ env:
         - PYTHONUNBUFFERED=1
         - PYTHONDONTWRITEBYTECODE=1
         - PIP_UPGRADE_STRATEGY=eager
+        # Don't get warnings about Python 2 support being deprecated. We
+        # know.
+        - PIP_NO_PYTHON_VERSION_WARNING=1
         - CC="ccache gcc"
         - CCACHE_NOCPP2=true
         - CCACHE_SLOPPINESS=file_macro,time_macros,include_file_ctime,include_file_mtime

appveyor.yml

@@ -17,6 +17,9 @@ environment:
     # too often we get failures to resolve DNS names or failures
     # to connect on AppVeyor.
     GEVENTTEST_USE_RESOURCES: "-network"
+    # Don't get warnings about Python 2 support being deprecated. We
+    # know.
+    PIP_NO_PYTHON_VERSION_WARNING: 1
     # Enable this if debugging a resource leak. Otherwise
     # it slows things down.
     # PYTHONTRACEMALLOC: 10