[Linux] dev_appserver.py ERROR module.py:1652] The PHP runtime cannot be run with the "Memcache" PECL extension installed @ Ubuntu 16.04

在 Ubuntu server 上，首推 https://cloud.google.com/sdk/downloads#linux 安裝法，不要靠 apt 套件管理，不然會踩到很多麻煩：

$ curl https://dl.google.com/dl/cloudsdk/channels/rapid/downloads/google-cloud-sdk-183.0.0-linux-x86_64.tar.gz | tar -xvf -
$ cd google-cloud-sdk
$ ./install.sh

裝完後，若是要運行 php-sdk 時，會踩到 php 環境問題，通常就是要指定 --php_executable_path 位置：

$ dev_appserver.py --enable_host_checking false --host 0.0.0.0 --port 8080  --php_executable_path /usr/bin/php-cgi5.6 app.yaml

只是執行時又會踩到缺套件等等的問題，裝到最後產生了 Memcache 套件問題，就要再把 Memcache 套件關閉即可：

$ php5.6 --ini
Configuration File (php.ini) Path: /etc/php/5.6/cli
Loaded Configuration File:         /etc/php/5.6/cli/php.ini
Scan for additional .ini files in: /etc/php/5.6/cli/conf.d
Additional .ini files parsed:      /etc/php/5.6/cli/conf.d/10-opcache.ini,
/etc/php/5.6/cli/conf.d/10-pdo.ini,
/etc/php/5.6/cli/conf.d/20-apcu.ini,
/etc/php/5.6/cli/conf.d/20-bcmath.ini,
/etc/php/5.6/cli/conf.d/20-calendar.ini,
/etc/php/5.6/cli/conf.d/20-ctype.ini,
/etc/php/5.6/cli/conf.d/20-exif.ini,
/etc/php/5.6/cli/conf.d/20-fileinfo.ini,
/etc/php/5.6/cli/conf.d/20-ftp.ini,
/etc/php/5.6/cli/conf.d/20-gettext.ini,
/etc/php/5.6/cli/conf.d/20-iconv.ini,
/etc/php/5.6/cli/conf.d/20-igbinary.ini,
/etc/php/5.6/cli/conf.d/20-json.ini,
/etc/php/5.6/cli/conf.d/20-memcache.ini,
/etc/php/5.6/cli/conf.d/20-msgpack.ini,
/etc/php/5.6/cli/conf.d/20-phar.ini,
/etc/php/5.6/cli/conf.d/20-posix.ini,
/etc/php/5.6/cli/conf.d/20-readline.ini,
/etc/php/5.6/cli/conf.d/20-shmop.ini,
/etc/php/5.6/cli/conf.d/20-sockets.ini,
/etc/php/5.6/cli/conf.d/20-sysvmsg.ini,
/etc/php/5.6/cli/conf.d/20-sysvsem.ini,
/etc/php/5.6/cli/conf.d/20-sysvshm.ini,
/etc/php/5.6/cli/conf.d/20-tokenizer.ini,
/etc/php/5.6/cli/conf.d/25-memcached.ini

$ sudo vim /etc/php/5.6/cli/conf.d/20-memcache.ini
; uncomment the next line to enable the module
;extension=memcache.so

$ sudo vim /etc/php/5.6/cli/conf.d/25-memcached.ini
; priority=25
;extension=memcached.so