Better error message for database read problems.

src/io.cpp

@@ -870,6 +870,10 @@ Pipeline SetPipeline(const PipelineOptions &values) {
         fs.seekg(0, fs.end);
         long length = fs.tellg();
         fs.seekg(0, fs.beg);
+        if (fs.fail()) {
+            std::cerr << "Error reading database! " << strerror(errno) << std::endl;
+            exit(1);
+        }
         std::cerr << "Reading " << length << " bytes of database" << std::endl;
         result.database = std::unique_ptr<unsigned char[]>(new unsigned char[length]);
         fs.read((char *)result.database.get(), length);

test/scripts/random-crap.sh

@@ -31,6 +31,10 @@ echo 'Issue #36: Cog and Attitude without Star-ID'
 echo 'Run the generator without centroids a whole bunch and make sure no assertions go off'
 ./lost pipeline --generate 200 --generate-perturb-centroids 5 --generate-centroids-only
 
+echo 'Error message for database that does not exist'
+no_database_out=$(./lost pipeline --generate 1 --database 'does not.exist' --star-id-algo py 2>&1) && exit 1
+[[ $no_database_out == 'Error reading database!'* ]] || exit 1
+
 echo 'Speed 95-th percentile should be different than max for 20 but not 19 trials'
 nineteen_out=$(./lost pipeline --generate 19 --generate-centroids-only --attitude-algo quest --print-speed -)
 nineteen_max_ns=$(echo "$nineteen_out" | grep total_max_ns | cut -d' ' -f2)