build: preprocess messages and assets in setup.py

This enforces presence of the trezor-common submodule, copies coins.json to the
package directory (from where we can install it with bdist) and if possible,
regenerates protobuf messages.

That currently doesn't work on Windows, because it's a shell script. Also it
relies on presence of `protoc` protobuf compiler. Therefore the regeneration
step is optional and converted protobuf messages should still be commited to
this repo.

coins.json, OTOH, is gitignored in trezorlib, and must be copied from
trezor-common every time. This works because sdist includes the vendor
directory.

.gitignore

@@ -14,3 +14,6 @@ docs/_build
 docs/.docs-build-environment
 .tox/
 .cache/
+.pytest_cache/
+
+trezorlib/coins.json

setup.py

@@ -1,5 +1,10 @@
 #!/usr/bin/env python3
-from setuptools import setup
+import os.path
+import shutil
+import subprocess
+
+from setuptools import setup, Command
+from setuptools.command.build_py import build_py
 
 install_requires = [
     'setuptools>=19.0',
@@ -24,6 +29,44 @@ else:
 
 from trezorlib import __version__ as VERSION
 
+
+class PrebuildCommand(Command):
+    description = 'update vendored files (coins.json, protobuf messages)'
+    user_options = []
+
+    TREZOR_COMMON = os.path.join('vendor', 'trezor-common')
+
+    def initialize_options(self):
+        pass
+
+    def finalize_options(self):
+        pass
+
+    def run(self):
+        # check for existence of the submodule directory
+        coins_json = os.path.join(self.TREZOR_COMMON, 'coins.json')
+        if not os.path.exists(coins_json):
+            raise Exception('trezor-common submodule seems to be missing.\n' +
+                            'Use "git submodule update --init" to retrieve it.')
+
+        # copy coins.json to the tree
+        shutil.copy(coins_json, 'trezorlib')
+
+        # regenerate messages
+        try:
+            subprocess.check_call(os.path.join(os.getcwd(), 'tools', 'build_protobuf'))
+        except Exception as e:
+            print(e)
+            print("Generating protobuf failed. Maybe you don't have 'protoc', or maybe you are on Windows?")
+            print("Using pre-generated files.")
+
+
+class CustomBuild(build_py):
+    def run(self):
+        self.run_command('prebuild')
+        super().run()
+
+
 setup(
     name='trezor',
     version=VERSION,
@@ -39,6 +82,9 @@ setup(
         'trezorlib.tests.device_tests',
         'trezorlib.tests.unit_tests',
     ],
+    package_data={
+        'trezorlib': ['coins.json'],
+    },
     scripts=['trezorctl'],
     install_requires=install_requires,
     python_requires='>=3.3',
@@ -51,4 +97,8 @@ setup(
         'Operating System :: MacOS :: MacOS X',
         'Programming Language :: Python :: 3 :: Only',
     ],
+    cmdclass={
+        'prebuild': PrebuildCommand,
+        'build_py': CustomBuild,
+    },
 )