Improve error handling

hpib.py

@@ -39,7 +39,11 @@ class GPIBProtocol(serial.threaded.LineReader):
             if "?" in command:
                 self.write_line("++read eoi")
                 # The command was a query, wait for response
-                line = self.responses.get(timeout=timeout)
+                try:
+                    line = self.responses.get(timeout=timeout)
+                except Empty:
+                    print("No frequency returned")
+                    return None
                 return line
             else:
                 pass

setup.py

@@ -12,7 +12,7 @@ meta = dict(name='hpib',
             entry_points= {
                 'console_scripts': ['trackDoppler=trackDoppler:main'],
             },
-            install_requires=['pyserial', 'astropy>=2.0']
+            install_requires=['pyserial']#, 'astropy>=2.0']
             )
 
 setup(**meta)