latex writer considers unitless dimensions as px based

CHANGES

@@ -15,6 +15,8 @@ Incompatible changes
   sphinxVerbatimintable which handles captions and wraps lines(ref #2704).
 * latex, replace ``pt`` by TeX equivalent ``bp`` if found in ``width`` or
   ``height`` attribute of an image.
+* latex, if ``width`` or ``height`` attribute of an image is given with no unit,
+  use ``px`` rather than ignore it.
 
 
 Features added

sphinx/writers/latex.py

@@ -283,12 +283,10 @@ def rstdim_to_latexdim(width_str):
     res = width_str
     amount, unit = match.groups()[:2]
     float(amount)  # validate amount is float
-    if not unit:
-        return None
+    if unit in ('', "px"):
+        res = "%s\\sphinxpxdimen" % amount
     elif unit == 'pt':
         res = '%sbp' % amount  # convert to 'bp'
-    elif unit == "px":
-        res = "%s\\sphinxpxdimen" % amount
     elif unit == "%":
         res = "%.3f\\linewidth" % (float(amount) / 100.0)
     return res

tests/test_writer_latex.py

@@ -25,7 +25,7 @@ def test_rstdim_to_latexdim():
     assert rstdim_to_latexdim('160pt') == '160bp'
     assert rstdim_to_latexdim('160pc') == '160pc'
     assert rstdim_to_latexdim('30%') == '0.300\\linewidth'
-    assert rstdim_to_latexdim('160') is None
+    assert rstdim_to_latexdim('160') == '160\\sphinxpxdimen'
 
     # flaot values
     assert rstdim_to_latexdim('160.0em') == '160.0em'