BaseTools: Refactor python except statements

Convert "except ... ," to "except ... as" to be compatible with python3.
Based on "futurize -f lib2to3.fixes.fix_except"

Contributed-under: TianoCore Contribution Agreement 1.1
Cc: Yonghong Zhu <yonghong.zhu@intel.com>
Cc: Liming Gao <liming.gao@intel.com>
Signed-off-by: Gary Lin <glin@suse.com>
Reviewed-by: Yonghong Zhu <yonghong.zhu@intel.com>

BaseTools/Scripts/PackageDocumentTools/plugins/EdkPlugins/basemodel/doxygen.py

@@ -115,7 +115,7 @@ class DoxygenFile(Page):
             f = open(self.mFilename, 'w')
             f.write('\n'.join(str))
             f.close()
-        except IOError, e:
+        except IOError as e:
             ErrorMsg ('Fail to write file %s' % self.mFilename)
             return False
 
@@ -429,7 +429,7 @@ class DoxygenConfigFile:
             f = open(path, 'w')
             f.write(text)
             f.close()
-        except IOError, e:
+        except IOError as e:
             ErrorMsg ('Fail to generate doxygen config file %s' % path)
             return False