Update return code for calc_navigation_measurement() python

Author: jacobmcnamee

python/swiftnav/track.pxd

@@ -181,9 +181,10 @@ cdef extern from "libswiftnav/track.h":
     gnss_signal_t sid
     u16 lock_counter
 
-  void calc_navigation_measurement(u8 n_channels, const channel_measurement_t *meas[],
-                                   navigation_measurement_t *nav_meas[],
-                                   const ephemeris_t* e[])
+  s8 calc_navigation_measurement(u8 n_channels, const channel_measurement_t *meas[],
+                                 navigation_measurement_t *nav_meas[],
+                                 const ephemeris_t* e[])
+
   int nav_meas_cmp(const void *a, const void *b)
   u8 tdcp_doppler(u8 n_new, navigation_measurement_t *m_new,
                   u8 n_old, navigation_measurement_t *m_old,