Hi,
it's an annoying problem.
The solution so far is to add a couple of lines in the header of each PO file,
for example the last two lines in this header
msgid ""
msgstr ""
"Project-Id-Version: Koha 18.05\n"
"POT-Creation-Date: 2018-05-10 00:54-0300\n"
"PO-Revision-Date: 2018-04-27 21:15+0000\n"
"Last-Translator: Zeno Tajoli <z.tajoli@cineca.it>\n"
"Language-Team: CILEA <z.tajoli@cineca.it>\n"
"Language: it\n"
"MIME-Version: 1.0\n"
"Content-Type: text/plain; charset=UTF-8\n"
"Content-Transfer-Encoding: 8bit\n"
"Plural-Forms: nplurals=2; plural=(n != 1);\n"
"X-Generator: Pootle 2.8\n"
"X-Poedit-SourceCharset: UTF-8\n"
"X-POOTLE-MTIME: 1524863755.089782\n"
"X-Pootle-Path: /it/18.05/it-IT-marc-MARC21.po\n"
"X-Pootle-Revision: 1\n"
X-Pootle-Path must have language code, project code and file name.
I fixed all headers for 18.05 files, I'm fixing all the others.
If you have already downloaded a file, please add the lines and try to upload it.
Regards
Bernardo
--
Bernardo Gonzalez Kriegel