Python3.8 on centos dance

shlax/actions/pip.py

@@ -10,6 +10,8 @@ class Pip(Action):
         super().__init__(*pip_packages, pip=pip, requirements=requirements)
 
     async def call(self, *args, **kwargs):
+        pip = self.kwargs.get('pip', None)
+        if not pip:
             pip = await self.which('pip3', 'pip', 'pip2')
             if pip:
                 pip = pip[0]
@@ -38,6 +40,7 @@ class Pip(Action):
         await self.exec(f'{pip} install --upgrade pip')
 
         # https://github.com/pypa/pip/issues/5599
+        if 'pip' not in self.kwargs:
             pip = 'python3 -m pip'
 
         source = [p for p in self.args if p.startswith('/') or p.startswith('.')]

shlaxfile.py

@@ -17,7 +17,7 @@ build = Buildah(
         '''),
         Copy('shlax/', 'setup.py', '/app'),
     ),
-    Pip('/app'),
+    Pip('/app', pip='python3.8 -m pip'),
     commit='yourlabs/shlax',
     workdir='/app',
 )