Re-install `pip` inside the venv

Close #685

README.md

@@ -72,6 +72,8 @@ is [pyflow], but it is written with Rust and thus can't get much help from the b
 
 PDM requires python version 3.7 or higher.
 
+### Via Install Script
+
 Like Pip, PDM provides an installation script that will install PDM into an isolated environment.
 
 **For Linux/Mac**
@@ -108,7 +110,7 @@ optional arguments:
 
 You can either pass the options after the script or set the env var value.
 
-## Alternative Installation Methods
+### Alternative Installation Methods
 
 If you are on MacOS and using `homebrew`, install it by:
 

README_zh.md

@@ -68,6 +68,8 @@ foo
 
 PDM 需要 Python 3.7 或更高版本。
 
+### 通过安装脚本
+
 像 pip 一样，PDM 也提供了一键安装脚本，用来将 PDM 安装在一个隔离的环境中。
 
 **Linux/Mac 安装命令**
@@ -104,7 +106,7 @@ optional arguments:
 
 你既可以通过直接增加选项，也可以通过设置对应的环境变量来达到这一效果。
 
-## 其他安装方法
+### 其他安装方法
 
 如果你使用的是 MacOS 并且安装了 `homebrew`：
 
@@ -112,7 +114,7 @@ optional arguments:
 $ brew install pdm
 ```
 
-如果你在Windows上使用 [Scoop](https://scoop.sh/), 运行以下命令安装：
+如果你在 Windows 上使用 [Scoop](https://scoop.sh/), 运行以下命令安装：
 
 ```
 PS> scoop bucket add frostming https://github.com/frostming/scoop-frostming.git

install-pdm.py

@@ -290,6 +290,10 @@ class Installer:
         else:
             venv_python = venv_path / "bin/python"
 
+        # Re-install the venv pip to ensure it's not DEBUNDLED
+        # See issue/685
+        _call_subprocess([str(venv_python), "-m", "pip", "install", "-IU", "pip"])
+
         if self.version:
             if self.version.upper() == "HEAD":
                 req = f"git+{REPO}.git@main#egg=pdm"

news/685.bugfix.md

+Fix the install script to ensure `pip` is not DEBUNDLED.