Backport PR #4868: Static path fixes

more use of the package dir instead of static file dir, and update a previous test patch of mine to work for build and install time tests

IPython/core/tests/test_display.py

@@ -48,6 +48,9 b' def test_image_filename_defaults():'
     nt.assert_raises(ValueError, display.Image)
     nt.assert_raises(ValueError, display.Image, data='this is not an image', format='badformat', embed=True)
     from IPython.html import DEFAULT_STATIC_FILES_PATH
+    # check boths paths to allow packages to test at build and install time
+    imgfile = os.path.join(tpath, 'html/static/base/images/ipynblogo.png')
+    if not os.path.exists(imgfile):
     imgfile = os.path.join(DEFAULT_STATIC_FILES_PATH, 'base/images/ipynblogo.png')
     img = display.Image(filename=imgfile)
     nt.assert_equal('png', img.format)

IPython/nbconvert/transformers/csshtmlheader.py

@@ -88,8 +88,9 b' class CSSHTMLHeaderTransformer(Transformer):'
         header = []
         
         #Construct path to IPy CSS
-        sheet_filename = os.path.join(path.get_ipython_package_dir(), 
-            'html', 'static', 'style', 'style.min.css')
+        from IPython.html import DEFAULT_STATIC_FILES_PATH
+        sheet_filename = os.path.join(DEFAULT_STATIC_FILES_PATH,
+            'style', 'style.min.css')
         
         #Load style CSS file.
         with io.open(sheet_filename, encoding='utf-8') as file: