fix: halt if pdf selected but unavailable (#4354)

* Related to #4326

If pdf output is selected but isn't available, then cve-bin-tool
tells you to install reportlab, but it was easy to miss that message as
the scan continued and pushed it off the screen.  This changes those
messages to be errors instead of info messages to increase visibility and 
reflect the new behaviour where cve-bin-tool will exit without doing a
scan if pdf is the only output mode selected.

---------

Signed-off-by: Terri Oda <terri.oda@intel.com>

cve_bin_tool/cli.py

@@ -63,6 +63,7 @@
     InsufficientArgs,
     InvalidExtensionError,
     MirrorError,
+    PDFOutputUnavailable,
     excepthook,
 )
 from cve_bin_tool.input_engine import InputEngine, TriageData
@@ -893,11 +894,14 @@ def main(argv=None):
 
     # Check for PDF support
     if "pdf" in output_formats and importlib.util.find_spec("reportlab") is None:
-        LOGGER.info("PDF output not available.")
-        LOGGER.info(
+        LOGGER.error("PDF output not available.")
+        LOGGER.error(
             "If you want to produce PDF output, please install reportlab using pip install reportlab"
         )
         output_formats.remove("pdf")
+        if len(output_formats) < 1:
+            # If there's no other formats selected, exit so people actually see the error
+            return ERROR_CODES[PDFOutputUnavailable]
 
     merged_reports = None
     if args["merge"]:

cve_bin_tool/error_handler.py

@@ -145,6 +145,10 @@ class NetworkConnectionError(Exception):
     """Raised when issue occurred with internet connection"""
 
 
+class PDFOutputUnavailable(Exception):
+    """Raised when reportlab is not installed and PDF output is unavailable"""
+
+
 class ErrorMode(Enum):
     Ignore = 0
     NoTrace = 1
@@ -246,4 +250,5 @@ def __exit__(self, exc_type, exc_val, exc_tb):
     InvalidExtensionError: 42,
     SigningError: 43,
     NetworkConnectionError: 44,
+    PDFOutputUnavailable: 45,
 }

test/test_cli.py

@@ -706,7 +706,7 @@ def test_console_output_depending_reportlab_existence(self, caplog):
 
         assert (
             "cve_bin_tool",
-            logging.INFO,
+            logging.ERROR,
             not_installed_msg,
         ) in caplog.record_tuples