Fix python build failure on Mac

Author: Kaixiang-AWS

ubuntu/python/3.7.1/Dockerfile

@@ -132,7 +132,7 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
     && wget -O python.tar.xz "https://www.python.org/ftp/python/${PYTHON_VERSION%%[a-z]*}/Python-$PYTHON_VERSION.tar.xz" \
 	&& wget -O python.tar.xz.asc "https://www.python.org/ftp/python/${PYTHON_VERSION%%[a-z]*}/Python-$PYTHON_VERSION.tar.xz.asc" \
 	&& export GNUPGHOME="$(mktemp -d)" \
-	&& (gpg --batch --keyserver ha.pool.sks-keyservers.net --recv-keys "$GPG_KEY" \
+	&& (gpg --batch --keyserver hkp://p80.pool.sks-keyservers.net:80 --recv-keys "$GPG_KEY" \
         || gpg --keyserver pgp.mit.edu --recv-keys "$GPG_KEY" \
         || gpg --keyserver keyserver.ubuntu.com --recv-keys "$GPG_KEY") \
 	&& gpg --batch --verify python.tar.xz.asc python.tar.xz \