Addon Manager: Refactor installation code

Improve testability of installation code by refactoring it to completely
separate the GUI and non-GUI code, and to provide more robust support
for non-GUI access to some type of Addon Manager activity.

src/Mod/AddonManager/manage_python_dependencies.py

@@ -94,39 +94,16 @@ def call_pip(args) -> List[str]:
         call_args.extend(args)
         proc = None
         try:
-            no_window_flag = 0
-            if hasattr(subprocess, "CREATE_NO_WINDOW"):
-                no_window_flag = subprocess.CREATE_NO_WINDOW  # Added in Python 3.7
-            proc = subprocess.run(
-                call_args,
-                stdout=subprocess.PIPE,
-                stderr=subprocess.PIPE,
-                check=True,
-                timeout=30,
-                creationflags=no_window_flag,
-            )
-            if proc.returncode != 0:
-                pip_failed = True
-        except subprocess.CalledProcessError as e:
-            pip_failed = True
-            print(e)
-        except subprocess.TimeoutExpired:
-            FreeCAD.Console.PrintWarning(
-                translate(
-                    "AddonsInstaller",
-                    "pip took longer than 30 seconds to return results, giving up on it",
-                )
-                + "\n"
-            )
-            FreeCAD.Console.PrintLog(" ".join(call_args))
+            proc = utils.run_interruptable_subprocess(call_args)
+        except subprocess.CalledProcessError:
             pip_failed = True
 
         result = []
         if not pip_failed:
-            data = proc.stdout.decode()
+            data = proc.stdout
             result = data.split("\n")
         elif proc:
-            raise PipFailed(proc.stderr.decode())
+            raise PipFailed(proc.stderr)
         else:
             raise PipFailed("pip timed out")
     else: