Don't bail on WindowsError not existing on non-windows systems.

Discussion see https://github.com/zopefoundation/Zope/commit/87c5992e7e40604df206bb713e42bafd5919fe64

src/Zope2/Startup/__init__.py

@@ -27,6 +27,12 @@ from ZConfig.components.logger import loghandler
 from zope.event import notify
 from zope.processlifetime import ProcessStarting
 
+try:
+    IO_ERRORS = (IOError, WindowsError)
+except NameError:
+    IO_ERRORS = (IOError,)
+
+
 logger = logging.getLogger("Zope")
 started = False
 
@@ -283,7 +289,7 @@ class ZopeStarter:
                 lock_file(self.lockfile)
                 self.lockfile.write(str(os.getpid()))
                 self.lockfile.flush()
-            except (IOError, WindowsError):
+            except IO_ERRORS:
                 pass
 
     def makePidFile(self):
@@ -295,7 +301,7 @@ class ZopeStarter:
                 f = open(self.cfg.pid_filename, 'w')
                 f.write(str(os.getpid()))
                 f.close()
-            except (IOError, WindowsError):
+            except IO_ERRORS:
                 pass
 
     def unlinkPidFile(self):