Check dependencies on setup in the nicer way. (#5989)

1 files changed, 7 insertions, 20 deletions

diff --git a/synapse/config/repository.py b/synapse/config/repository.py

index fdb1f246d0..34f1a9a92d 100644
--- a/synapse/config/repository.py
+++ b/synapse/config/repository.py
@@ -16,6 +16,7 @@
 import os
 from collections import namedtuple
 
+from synapse.python_dependencies import DependencyException, check_requirements
 from synapse.util.module_loader import load_module
 
 from ._base import Config, ConfigError
@@ -34,17 +35,6 @@ THUMBNAIL_SIZE_YAML = """\
         #    method: %(method)s
 """
 
-MISSING_NETADDR = "Missing netaddr library. This is required for URL preview API."
-
-MISSING_LXML = """Missing lxml library. This is required for URL preview API.
-
-    Install by running:
-        pip install lxml
-
-    Requires libxslt1-dev system package.
-    """
-
-
 ThumbnailRequirement = namedtuple(
     "ThumbnailRequirement", ["width", "height", "method", "media_type"]
 )
@@ -171,16 +161,10 @@ class ContentRepositoryConfig(Config):
         self.url_preview_enabled = config.get("url_preview_enabled", False)
         if self.url_preview_enabled:
             try:
-                import lxml
-
-                lxml  # To stop unused lint.
-            except ImportError:
-                raise ConfigError(MISSING_LXML)
+                check_requirements("url_preview")
 
-            try:
-                from netaddr import IPSet
-            except ImportError:
-                raise ConfigError(MISSING_NETADDR)
+            except DependencyException as e:
+                raise ConfigError(e.message)
 
             if "url_preview_ip_range_blacklist" not in config:
                 raise ConfigError(
@@ -189,6 +173,9 @@ class ContentRepositoryConfig(Config):
                     "to work"
                 )
 
+            # netaddr is a dependency for url_preview
+            from netaddr import IPSet
+
             self.url_preview_ip_range_blacklist = IPSet(
                 config["url_preview_ip_range_blacklist"]
             )