BusinessTemplate: Import Big File's data property as Pdata

When i upgrade/install erp5_notebook in an instance which use neo storage instead
of zeo, Neo stopped immediately, as consequence, erp5_notebook can't be installed/upgraded.

The reason is in erp5_notebook, there has a one big file scipy.data.bin 157MB [1] which can't be
installed as it is  in neo. The solution suggested by @jm is to wrapper it by Pdata when install
a BT5.

See merge request !953

[1] https://lab.nexedi.com/nexedi/erp5-bin/blob/7d3505fd/bt5/erp5_notebook/SkinTemplateItem/portal_skins/erp5_notebook/scipy.data.bin

bt5/erp5_core_test/TestTemplateItem/portal_components/test.erp5.testBusinessTemplate.py

@@ -46,6 +46,7 @@ import string
 import tempfile
 import glob
 import sys
+from OFS.Image import Pdata
 
 WORKFLOW_TYPE = 'erp5_workflow'
 
@@ -7262,8 +7263,14 @@ class TestBusinessTemplate(BusinessTemplateMixin):
     self.assertEqual(file_content, expected_file_content)
     self.assertEqual(len(file_content), len(expected_file_content))
 
+  def stepCheckFileisImportedAsPdata(self, sequence=None, **kw):
+    self.assertIsInstance(self.portal.portal_templates
+      .getInstalledBusinessTemplate('erp5_xhtml_style')._skin_item._objects
+      ['portal_skins/erp5_ckeditor/ckeditor/LICENSE.md'].data, Pdata)
+
   def test_text_file_import_export(self):
     """
+    First Check if file is imported as Pdata, then check the following case:
     When importing back ace.js containing a last line with whitespaces only,
     the last line was not imported, and thus the file could never been
     downloaded completely as its really size was less than the one on the File
@@ -7271,6 +7278,8 @@ class TestBusinessTemplate(BusinessTemplateMixin):
     """
     sequence_list = SequenceList()
     sequence_string = """
+       CheckFileisImportedAsPdata
+
        CreateSkinFolder
        CreateTextFile
        CheckTextFileContent

product/ERP5/Document/BusinessTemplate.py

@@ -99,6 +99,7 @@ from ZODB.broken import Broken, BrokenModified
 from Products.ERP5.genbt5list import BusinessTemplateRevision, \
   item_name_list, item_set
 from Products.ERP5Type.mixin.component import ComponentMixin
+from OFS.Image import File as OFSFile
 
 CACHE_DATABASE_PATH = None
 try:
@@ -878,6 +879,8 @@ class ObjectTemplateItem(BaseTemplateItem):
     # backward-compatibility
     elif six.PY3 and is_text:
       data = data.decode('utf-8')
+    if isinstance(obj, OFSFile) and property_name == "data":
+      data = obj._read_data(data)[0]
     try:
       setattr(obj, property_name, data)
     except BrokenModified: