Better py2/py3 compatibility

cadquery/occ_impl/exporters.py

@@ -1,3 +1,4 @@
+from __future__ import unicode_literals
 from OCC.Visualization import Tesselator
 
 import cadquery
@@ -119,7 +120,7 @@ def readAndDeleteFile(fileName):
     """
     res = ""
     with open(fileName, 'r') as f:
-        res = f.read()
+        res = "{}".format(f.read())
 
     os.remove(fileName)
     return res
@@ -183,8 +184,8 @@ class AmfWriter(object):
             v2.text = str(t[1])
             v3 = ET.SubElement(triangle, 'v3')
             v3.text = str(t[2])
-
+        
-        ET.ElementTree(amf).write(outFile, encoding='ISO-8859-1')
+        amf = ET.ElementTree(amf).write(outFile, xml_declaration=True)
 
 
 """

tests/TestExporters.py

@@ -3,10 +3,7 @@
 """
 # core modules
 import sys
-if sys.version_info.major == 2:
+import io
-    import cStringIO as StringIO
-else:
-    import io as StringIO
 
 # my modules
 from cadquery import *
@@ -23,10 +20,15 @@ class TestExporters(BaseTest):
             returns the result in case the case wants to do more checks also
         """
         p = Workplane("XY").box(1, 2, 3)
-        s = StringIO.StringIO()
+
+        if eType ==  exporters.ExportTypes.AMF:
+            s = io.BytesIO()
+        else:
+            s = io.StringIO()
+        
         exporters.exportShape(p, eType, s, 0.1)
 
-        result = s.getvalue()
+        result = '{}'.format(s.getvalue())
 
         for q in stringsToFind:
             self.assertTrue(result.find(q) > -1)