App.os_release: cat os-release non-interactively

Even with --interactive=[true|auto], there's no point in trying to
read /etc/os-release interactively, so don't do that. Most notably,
this commit keeps the property method from spilling /etc/os-release's
content over the terminal.

Signed-off-by: Jan Lindemann <jan@janware.com>

src/python/jw/pkg/App.py

@@ -18,6 +18,7 @@ from enum import Enum, auto
 from .lib.App import App as Base
 from .lib.log import *
 from .lib.Distro import Distro
+from .lib.ExecContext import InputMode
 
 # Meaning of pkg.requires.xxx variables
 # build: needs to be built and installed before this can be built
@@ -299,7 +300,13 @@ class App(Base):
     @property
     def os_release(self) -> str:
         if self.__os_release is None:
-            result = self.call_async(self.exec_context.run(['/usr/bin/cat', '/etc/os-release'], throw=True))
+            result = self.call_async(
+                        self.exec_context.run(
+                            ['/usr/bin/cat', '/etc/os-release'],
+                            throw=True,
+                            cmd_input=InputMode.NonInteractive
+                        )
+                    )
             assert result.status == 0
             self.__os_release = result.decode().stdout.strip()
         return self.__os_release