pip is configured with locations that require TLS/SSL, however the ssl module in Python is not
系统是centos7.2
python3.6.2
问题描述
第一遍编译安装Python3.6的步骤如下：
#先安装相关包：
yum install zlib-devel bzip2-devel openssl-devel ncurses-devel sqlite-devel readline-devel tk-devel gcc make
#下载并编译Python3：
wget https://www.python.org/ftp/python/3.6.2/Python-3.6.2.tar.xz
tar -xvJf Python-3.6.2.tar.xz
cd Python-3.6.2
./configure prefix=/usr/local/python3
make && make install
mv /usr/bin/python /usr/bin/python.bak #备份原Python
ln -s /usr/local/python3/bin/python3 /usr/bin/python #让Python命令指向新编译的python3
python -V #确认该命令是否指向python3
python2 -V #确认该命令是否指向原python2.7.5
因为执行yum需要python2版本，所以我们还要修改yum的配置，执行：
vi /usr/bin/yum
把#! /usr/bin/python修改为#! /usr/bin/python2
同理修改/usr/libexec/urlgrabber-ext-down
-------------------------------------------------------------------------
到此，Python3确实是安装成功了，也能与2.7.5版并存。
但接下来通过pip（注：因为是Python3，所以实际使用pip3命令）安装pymysql、requests时提示错误：
pip is configured with locations that require TLS/SSL, however the ssl module in Python is not available.
#pip3 install pymysql
pip is configured with locations that require TLS/SSL, however the ssl module in Python is not available.
Collecting pymysql
Could not fetch URL https://pypi.python.org/simple/pymysql/: There was a problem confirming the ssl certificate: Can't connect to HTTPS URL because the SSL module is not available. - skipping
Could not find a version that satisfies the requirement pymysql (from versions: )
No matching distribution found for pymysql
网上查找资料，第一种方案提示说，需要在make前，./configure那一步加一个“--with-ssl”的参数，但实际执行"./configure --with-ssl"后提示“configure: WARNING: unrecognized options: --with-ssl”。
==============划重点！==============
后来找到第二种方案，实测可行，需要在make前修改Modules/Setup文件，完整编译步骤如下：
cd Python-3.6.2
make clean #如果已经和我一样编译过一次，建议先执行此步骤，否则可省略。
./configure prefix=/usr/local/python3
修改./Modules/Setup文件（将如下四行的注释去掉）：
# Socket module helper for SSL support; you must comment out the other
# socket line above, and possibly edit the SSL variable:
SSL=/usr/local/ssl
_ssl _ssl.c \
-DUSE_SSL -I$(SSL)/include -I$(SSL)/include/openssl \
-L$(SSL)/lib -lssl -lcrypto
此外，因为用到的lib路径是/usr/local/ssl，而默认情况下，编译器只会使用/lib和/usr/lib这两个目录下的库文件，所以还需要做以下事情：
vim /etc/ld.so.conf（这个文件记录了编译时使用的动态链接库的路径）
增加一行：/usr/local/ssl/lib（注：也可能已有，只需把双引号去掉）
并执行 /sbin/ldconfig -v命令
make && make install
到此Python3重新编译成功，并且再通过pip3安装pymysql、requests等库就不会提示如标题的错误了。
最后，执行Python操作数据库的脚本，验证一下环境是否正确。
