Use modern Python exception syntax

"except Exception as e" instead of "except Exception, e"

This is part of a transition to supporting Python 3.  Python >= 2.6
support "as" syntax.

Note: this removes Python 2.5 support.

Change-Id: I309599f3981bba2b46111c43102bee38ff132803
diff --git a/project.py b/project.py
index 472b1d3..96feb94 100644
--- a/project.py
+++ b/project.py
@@ -1044,7 +1044,7 @@
 
       try:
         self._Checkout(revid, quiet=True)
-      except GitError, e:
+      except GitError as e:
         syncbuf.fail(self, e)
         return
       self._CopyFiles()
@@ -1066,7 +1066,7 @@
                    branch.name)
       try:
         self._Checkout(revid, quiet=True)
-      except GitError, e:
+      except GitError as e:
         syncbuf.fail(self, e)
         return
       self._CopyFiles()
@@ -1151,7 +1151,7 @@
       try:
         self._ResetHard(revid)
         self._CopyFiles()
-      except GitError, e:
+      except GitError as e:
         syncbuf.fail(self, e)
         return
     else:
@@ -1723,7 +1723,7 @@
           continue
       try:
         os.symlink(os.path.relpath(stock_hook, os.path.dirname(dst)), dst)
-      except OSError, e:
+      except OSError as e:
         if e.errno == errno.EPERM:
           raise GitError('filesystem must support symlinks')
         else:
@@ -1786,7 +1786,7 @@
             os.symlink(os.path.relpath(src, os.path.dirname(dst)), dst)
           else:
             raise GitError('cannot overwrite a local work tree')
-        except OSError, e:
+        except OSError as e:
           if e.errno == errno.EPERM:
             raise GitError('filesystem must support symlinks')
           else: