环境: Arch Linux 
版本: Python 3.12.6, pip 24.2 
编辑器: Cursor 
我在 Cursor 内集成终端通过以下命令创建并激活了虚拟环境: 
python3 -m venv .venv
source .venv/bin/activate

此时已出现 (.venv) 激活成功标识. 
但当我执行 pip install fastapi 时出现以下报错: 

error: externally-managed-environment
× This environment is externally managed 
╰─> To install Python packages system-wide, try ‘pacman -S 
python-xyz’, where xyz is the package you are trying to 
in...