BaseTools: Handle the bytes and str difference

Deal with bytes and str is different, remove the unicode(),
correct open file parameter.
Using utcfromtimestamp instead of fromtimestamp.

Cc: Bob Feng <bob.c.feng@intel.com>
Cc: Liming Gao <liming.gao@intel.com>
Cc: Yonghong Zhu <yonghong.zhu@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Zhiju.Fan <zhijux.fan@intel.com>
Tested-by: Laszlo Ersek <lersek@redhat.com>
Tested-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Liming Gao <liming.gao@intel.com>
Reviewed-by: Bob Feng <bob.c.feng@intel.com>

BaseTools/Source/Python/Common/LongFilePathSupport.py

@@ -49,15 +49,3 @@ def CopyLongFilePath(src, dst):
     with open(LongFilePath(src), 'rb') as fsrc:
         with open(LongFilePath(dst), 'wb') as fdst:
             shutil.copyfileobj(fsrc, fdst)
-
-## Convert a python unicode string to a normal string
-#
-# Convert a python unicode string to a normal string
-# UniToStr(u'I am a string') is 'I am a string'
-#
-# @param Uni:  The python unicode string
-#
-# @retval:     The formatted normal string
-#
-def UniToStr(Uni):
-    return repr(Uni)[2:-1]