src/sage/doctest/util.py: put "import" inside the "try"

We're importing psutil and trying to catch the ImportError if one is
raised. But for that to work, it helps to put "import" inside of the
"try" block.

src/sage/doctest/util.py

@@ -301,14 +301,18 @@ def _quick_cputime(self, expect_objects):
                     # installed as a transitive dependency (ipython
                     # needs it), but it isn't explicitly listed as
                     # a dependency of sagelib.
-                    from psutil import NoSuchProcess, Process, ZombieProcess
                     try:
-                        cputime += sum(Process(S.pid()).cpu_times()[0:2])
-                    except (ImportError, ValueError, NoSuchProcess, ZombieProcess):
-                        # ImportError: no psutil
-                        # ValueError: invalid (e.g. negative) PID
-                        # NoSuchProcess: it's gone
-                        # ZombieProcess: PID refers to a zombie
+                        from psutil import (NoSuchProcess,
+                                            Process,
+                                            ZombieProcess)
+                        try:
+                            cputime += sum(Process(S.pid()).cpu_times()[0:2])
+                        except (ValueError, NoSuchProcess, ZombieProcess):
+                            # ValueError: invalid (e.g. negative) PID
+                            # NoSuchProcess: it's gone
+                            # ZombieProcess: PID refers to a zombie
+                            pass
+                    except ImportError:
                         pass
 
         return cputime