feat: add message about mirror when nvd is down

cve_bin_tool/data_sources/nvd_source.py

@@ -413,15 +413,24 @@ async def fetch_cves(self):
                 self.nist_fetch_using_api(),
             )
         else:
-            nvd_metadata = await asyncio.create_task(
-                self.nist_scrape(self.session),
-            )
+            try:
+                nvd_metadata = await asyncio.create_task(
+                    self.nist_scrape(self.session),
+                )
+
+                tasks = [
+                    self.cache_update(self.session, url, meta["sha256"])
+                    for url, meta in nvd_metadata.items()
+                    if meta is not None
+                ]
+            except Exception as e:
+                self.nvd_type = "api2"
+                self.feed = self.FEED_MIRROR
+                self.LOGGER.info("NVD appears to be down, falling back to mirror")
+                self.all_cve_entries = await asyncio.create_task(
+                    self.nist_fetch_using_api(),
+                )
 
-            tasks = [
-                self.cache_update(self.session, url, meta["sha256"])
-                for url, meta in nvd_metadata.items()
-                if meta is not None
-            ]
 
         total_tasks = len(tasks)
 
@@ -464,14 +473,17 @@ async def nist_fetch_using_api(self) -> list:
             api_key=self.nvd_api_key,
             api_version=api_version,
         )
-        if self.incremental_update:
-            await nvd_api.get_nvd_params(
-                time_of_last_update=datetime.datetime.fromtimestamp(
-                    db.get_db_update_date()
+        try:
+            if self.incremental_update:
+                await nvd_api.get_nvd_params(
+                    time_of_last_update=datetime.datetime.fromtimestamp(
+                        db.get_db_update_date()
+                    )
                 )
-            )
-        else:
-            await nvd_api.get_nvd_params()
+            else:
+                await nvd_api.get_nvd_params()
+        except Exception as e:
+            self.LOGGER.debug(f"{e}")
         await nvd_api.get()
         await nvd_api.session.close()
         nvd_api.session = None