resolves #101: No longer assumes a date will always be present in the metadata and falls back by displayed "Unknown" in the Nd2 repr

Makefile

@@ -26,7 +26,7 @@ test:	build
 	docker run --rm -it jimrybarski/nd2reader python3.4 /opt/nd2reader/tests.py
 	docker run --rm -it jimrybarski/nd2reader python2.7 /opt/nd2reader/tests.py
 
-functest:	build
+ftest:	build
 	docker run --rm -v ~/nd2s:/var/nd2s -it jimrybarski/nd2reader python3.4 /opt/nd2reader/ftests.py
 	docker run --rm -v ~/nd2s:/var/nd2s -it jimrybarski/nd2reader python2.7 /opt/nd2reader/ftests.py
 	

nd2reader/interface.py

@@ -28,7 +28,7 @@ class Nd2(object):
         
     def __repr__(self):
         return "\n".join(["<ND2 %s>" % self._filename,
-                          "Created: %s" % self.date,
+                          "Created: %s" % self.date if self.date is not None else "Unknown",
                           "Image size: %sx%s (HxW)" % (self.height, self.width),
                           "Frames: %s" % len(self.frames),
                           "Channels: %s" % ", ".join(["'%s'" % str(channel) for channel in self.channels]),

nd2reader/model/metadata.py

@@ -35,7 +35,7 @@ class Metadata(object):
         """
         The date and time when acquisition began.
 
-        :rtype: datetime.datetime()
+        :rtype: datetime.datetime() or None
 
         """
         return self._date

nd2reader/parser/v3.py

@@ -59,7 +59,7 @@ class V3Parser(BaseParser):
         """
         The date and time when acquisition began.
 
-        :rtype: datetime.datetime()
+        :rtype: datetime.datetime() or None
 
         """
         for line in metadata_dict[six.b('ImageTextInfo')][six.b('SLxImageTextInfo')].values():
@@ -78,7 +78,7 @@ class V3Parser(BaseParser):
             if not absolute_start_12 and not absolute_start_24:
                 continue
             return absolute_start_12 if absolute_start_12 else absolute_start_24
-        raise ValueError("This ND2 has no recorded start time. This is probably a bug.")
+        return None
 
     def _parse_channels(self, metadata_dict):
         """