尝试在虚拟环境中安装Python包pip3时，我有以下警告：
警告是什么意思？我该如何解决？
请记住我正在学习Django并尝试设置MySQL数据库，所以请回答你的问题非常详细。
还要记住我使用Downloading/unpacking mysqlclient (from -r requirements.txt (line 2))
Downloading mysqlclient-1.3.7.tar.gz (79kB): 79kB downloaded
Running setup.py (path:/Users/owen/src/projects/mysite/build/mysqlclient/setup.py) egg_info for package mysqlclient
Installing collected packages: mysqlclient
Running setup.py install for mysqlclient
building '_mysql' extension
clang -Wno-unused-result -fno-common -dynamic -DNDEBUG -g -fwrapv -O3 -Wall -Wstrict-prototypes -I/usr/local/include -I/usr/local/opt/sqlite/include -Dversion_info=(1,3,7,'final',1) -D__version__=1.3.7 -I/usr/local/Cellar/mysql/5.6.20_1/include/mysql -I/usr/local/Cellar/python3/3.4.2_1/Frameworks/Python.framework/Versions/3.4/include/python3.4m -c _mysql.c -o build/temp.macosx-10.10-x86_64-3.4/_mysql.o -Os -g -fno-strict-aliasing
In file included from _mysql.c:40:
In file included from /usr/local/Cellar/python3/3.4.2_1/Frameworks/Python.framework/Versions/3.4/include/python3.4m/Python.h:8:
/usr/local/Cellar/python3/3.4.2_1/Frameworks/Python.framework/Versions/3.4/include/python3.4m/pyconfig.h:554:9: warning: 'HAVE_MBRTOWC' macro redefined [-Wmacro-redefined]
#define HAVE_MBRTOWC 1
^
/usr/local/Cellar/mysql/5.6.20_1/include/mysql/my_config.h:441:9: note: previous definition is here
#define HAVE_MBRTOWC
^
1 warning generated.
clang -bundle -undefined dynamic_lookup -L/usr/local/lib -L/usr/local/opt/sqlite/lib build/temp.macosx-10.10-x86_64-3.4/_mysql.o -L/usr/local/Cellar/mysql/5.6.20_1/lib -lmysqlclient_r -lssl -lcrypto -o build/lib.macosx-10.10-x86_64-3.4/_mysql.so
Successfully installed mysqlclient
Cleaning up...
来安装软件包。
------------ Deploying frontend ------------
Preparing to deploy:
Created staging directory at: 'C:\Users\RITHVI~1\AppData\Local\Temp\appcfg7427034133744005110.tmp'
Scanning for jsp files.
Generated git repository information file.
Scanning files on local disk.
Initiating update.
Cloning 3 static files.
Cloning 168 application files.
Deploying:
Uploading 0 files.
Initializing precompilation...
Deploying new version.
Closing update: new version is ready to start serving.
Uploading index definitions.
Deployment completed successfully