Switch from SKS to Ubuntu keyserver

See also https://github.com/docker-library/faq#openpgp--gnupg-keys-and-verification and https://github.com/tianon/pgp-happy-eyeballs

Author: tianon

7.3/alpine3.13/cli/Dockerfile

@@ -80,7 +80,7 @@ RUN set -eux; \
 		curl -fsSL -o php.tar.xz.asc "$PHP_ASC_URL"; \
 		export GNUPGHOME="$(mktemp -d)"; \
 		for key in $GPG_KEYS; do \
-			gpg --batch --keyserver ha.pool.sks-keyservers.net --recv-keys "$key"; \
+			gpg --batch --keyserver keyserver.ubuntu.com --recv-keys "$key"; \
 		done; \
 		gpg --batch --verify php.tar.xz.asc php.tar.xz; \
 		gpgconf --kill all; \

7.3/alpine3.13/fpm/Dockerfile

@@ -83,7 +83,7 @@ RUN set -eux; \
 		curl -fsSL -o php.tar.xz.asc "$PHP_ASC_URL"; \
 		export GNUPGHOME="$(mktemp -d)"; \
 		for key in $GPG_KEYS; do \
-			gpg --batch --keyserver ha.pool.sks-keyservers.net --recv-keys "$key"; \
+			gpg --batch --keyserver keyserver.ubuntu.com --recv-keys "$key"; \
 		done; \
 		gpg --batch --verify php.tar.xz.asc php.tar.xz; \
 		gpgconf --kill all; \