Check the existance and versions of necessary modules when starting synapse, log which modules are used

synapse/python_dependencies.py

@@ -0,0 +1,80 @@
+import logging
+from distutils.version import LooseVersion
+
+logger = logging.getLogger(__name__)
+
+REQUIREMENTS = {
+    "syutil==0.0.2": ["syutil"],
+    "matrix_angular_sdk==0.6.0": ["syweb==0.6.0"],
+    "Twisted>=14.0.0": ["twisted>=14.0.0"],
+    "service_identity>=1.0.0": ["service_identity>=1.0.0"],
+    "pyopenssl>=0.14": ["OpenSSL>=0.14"],
+    "pyyaml": ["yaml"],
+    "pyasn1": ["pyasn1"],
+    "pynacl": ["nacl"],
+    "daemonize": ["daemonize"],
+    "py-bcrypt": ["bcrypt"],
+    "frozendict>=0.4": ["frozendict"],
+    "pillow": ["PIL"],
+}
+
+
+class MissingRequirementError(Exception):
+    pass
+
+
+def check_requirements():
+    """Checks that all the modules needed by synapse have been correctly
+    installed and are at the correct version"""
+    for dependency, module_requirements in REQUIREMENTS.items():
+        for module_requirement in module_requirements:
+            if ">=" in module_requirement:
+                module_name, required_version = module_requirement.split(">=")
+                version_test = ">="
+            elif "==" in module_requirement:
+                module_name, required_version = module_requirement.split("==")
+                version_test = "=="
+            else:
+                module_name = module_requirement
+                version_test = None
+
+            try:
+                module = __import__(module_name)
+            except ImportError:
+                logging.exception(
+                    "Can't import %r which is part of %r",
+                    module_name, dependency
+                )
+                raise MissingRequirementError(
+                    "Can't import %r which is part of %r"
+                    % (module_name, dependency)
+                )
+            version = getattr(module, "__version__", None)
+            file_path = getattr(module, "__file__", None)
+            logger.info(
+                "Using %r version %r from %r to satisfy %r",
+                module_name, version, file_path, dependency
+            )
+
+            if version_test == ">=":
+                if version is None:
+                    raise MissingRequirementError(
+                        "Version of %r isn't set as __version__ of module %r"
+                        % (dependency, module_name)
+                    )
+                if LooseVersion(version) < LooseVersion(required_version):
+                    raise MissingRequirementError(
+                        "Version of %r in %r is too old. %r < %r"
+                        % (dependency, file_path, version, required_version)
+                    )
+            elif version_test == "==":
+                if version is None:
+                    raise MissingRequirementError(
+                        "Version of %r isn't set as __version__ of module %r"
+                        % (dependency, module_name)
+                    )
+                if LooseVersion(version) != LooseVersion(required_version):
+                    raise MissingRequirementError(
+                        "Unexpected version of %r in %r. %r != %r"
+                        % (dependency, file_path, version, required_version)
+                    )