import re
s = """ s_Tmp = 'ERROR: month "' | s_Month | '" not valid - ABORT' | CHAR(13) | CHAR(10) ;"""
res = re.sub(r"^(\s*)(.*)", lambda x: "{}{}".format(x.group(1), x.group(2).replace("\t", " ")), s, re.S)
print(res)
aW1wb3J0IHJlCnMgPSAiIiIgIAkJc19UbXAgCT0gJ0VSUk9SOiBtb250aCAiJyB8IHNfTW9udGggIAkJCQkgfAkJICciIG5vdCB2YWxpZCAtIEFCT1JUJyB8IENIQVIoMTMpIHwgQ0hBUigxMCkgOyIiIgpyZXMgPSByZS5zdWIociJeKFxzKikoLiopIiwgbGFtYmRhIHg6ICJ7fXt9Ii5mb3JtYXQoeC5ncm91cCgxKSwgeC5ncm91cCgyKS5yZXBsYWNlKCJcdCIsICIgIikpLCBzLCByZS5TKQpwcmludChyZXMp