Added binaryen not installed protections

Author: jonathanharg

binaryen/lib.py

@@ -2,11 +2,38 @@
 from typing import Any, cast
 from ._binaryen_cffi import ffi
 
+__macos_error = """You either do not have the binaryen library installed, or it is not in your standard C library path.
+
+Recommended: Using the brew package manager (https://brew.sh/) run brew install binaryen
+
+Alternatively add the precompiled libbinaryen.dylib from https://github.com/WebAssembly/binaryen/releases to your path.
+"""
+
+__windows_error = """You either do not have the binaryen library installed, or it is not in your standard C library path.
+
+Add the precompiled libbinaryen.dll from https://github.com/WebAssembly/binaryen/releases to your path.
+"""
+
+__linux_error = """You either do not have the binaryen library installed, or it is not in your standard C library path.
+
+Recommended: Use your distributions package manager to install binaryen.
+
+Alternatively add the precompiled libbinaryen.so from https://github.com/WebAssembly/binaryen/releases to your path.
+"""
+
 __lib_string = ""
+__error_message = ""
 if platform.system() == "Linux":
+    __error_message = __linux_error
     __lib_string = "libbinaryen.so"
 if platform.system() == "Windows":
+    __error_message = __windows_error
     __lib_string = "libbinaryen.dll"
 if platform.system() == "Darwin":
+    __error_message = __macos_error
     __lib_string = "libbinaryen.dylib"
-lib = cast(Any, ffi.dlopen(__lib_string))
+
+try:
+    lib = cast(Any, ffi.dlopen(__lib_string))
+except OSError as error:
+    raise OSError(__error_message) from error