handle bad gateway errors with custom exception

Author: davidhamann

fmrest/exceptions.py

@@ -57,5 +57,13 @@ class FileMakerError(FMRestException):
     def __init__(self, error_code: Optional[int], error_message: str) -> None:
         super().__init__('FileMaker Server returned error {}, {}'.format(error_code, error_message))
 
+
+class BadGatewayError(FMRestException):
+    """Exception for Bad Gateway errors from FMS's web server.
+    Usually, this happens when the web server is running, but the Data API is
+    not enabled or not responding.
+    """
+
+
 class RecordError(FMRestException):
     """Error with the local Record instance."""

fmrest/server.py

@@ -9,7 +9,7 @@
                     filename_from_url, PlaceholderDict)
 from .const import (PORTAL_PREFIX, FMSErrorCode, API_VERSIONS, API_DATE_FORMATS, API_PATH_PREFIX,
                     API_PATH)
-from .exceptions import BadJSON, FileMakerError, RecordError
+from .exceptions import BadJSON, FileMakerError, RecordError, BadGatewayError
 from .record import Record
 from .foundset import Foundset
 
@@ -132,7 +132,8 @@ def __enter__(self) -> 'Server':
         return self
 
     def __exit__(self, exc_type, exc_val, exc_traceback) -> None:
-        self.logout()
+        if self._token:
+            self.logout()
 
     def __repr__(self) -> str:
         return '<Server logged_in={} database={} layout={}>'.format(
@@ -921,6 +922,10 @@ def _call_filemaker(self, method: str, path: str,
                            proxies=self.proxies,
                            **kwargs)
 
+        if response.status_code == 502:
+            raise BadGatewayError("Web server responded with a Bad Gateway "
+                                  "error. Check if the Data API is enabled "
+                                  "and responding.")
         try:
             response_data = response.json()
         except json.decoder.JSONDecodeError as ex: