Consolidate raising a DependencyException() if required but not-found

This is now done by find_external_dependency() in all cases

I can't help but think this perhaps should be in a few more places...

mesonbuild/dependencies/base.py

@@ -392,8 +392,6 @@ class ConfigToolDependency(ExternalDependency):
                 mlog.log('Found', mlog.bold(self.tool_name), repr(req_version),
                          mlog.red('NO'))
             mlog.log('Dependency', mlog.bold(self.name), 'found:', mlog.red('NO'))
-            if self.required:
-                raise DependencyException('Dependency {} not found'.format(self.name))
             return False
         mlog.log('Found {}:'.format(self.tool_name), mlog.bold(shutil.which(self.config)),
                  '({})'.format(version))
@@ -475,9 +473,6 @@ class PkgConfigDependency(ExternalDependency):
                    '{!r}'.format(name, self.pkgbin.get_path()))
         ret, self.version = self._call_pkgbin(['--modversion', name])
         if ret != 0:
-            if self.required:
-                raise DependencyException('{} dependency {!r} not found'
-                                          ''.format(self.type_string, name))
             return
         found_msg = [self.type_string + ' dependency', mlog.bold(name), 'found:']
         if self.version_reqs is None:
@@ -826,8 +821,6 @@ class DubDependency(ExternalDependency):
         ret, res = self._call_dubbin(['describe', name])
 
         if ret != 0:
-            if self.required:
-                raise DependencyException('Dependency {!r} not found'.format(name))
             self.is_found = False
             mlog.log('Dependency', mlog.bold(name), 'found:', mlog.red('NO'))
             return
@@ -840,8 +833,6 @@ class DubDependency(ExternalDependency):
                     msg = ['Dependency', mlog.bold(name), 'found but it was compiled with']
                     msg += [mlog.bold(j['compiler']), 'and we are using', mlog.bold(comp)]
                     mlog.error(*msg)
-                    if self.required:
-                        raise DependencyException('Dependency {!r} not found'.format(name))
                     self.is_found = False
                     mlog.log('Dependency', mlog.bold(name), 'found:', mlog.red('NO'))
                     return
@@ -897,8 +888,6 @@ class DubDependency(ExternalDependency):
             self.link_args.append(file)
 
         if not found:
-            if self.required:
-                raise DependencyException('Dependency {!r} not found'.format(name))
             self.is_found = False
             mlog.log('Dependency', mlog.bold(name), 'found:', mlog.red('NO'))
             return
@@ -1249,8 +1238,6 @@ class ExtraFrameworkDependency(ExternalDependency):
                 self.name = d
                 self.is_found = True
                 return
-        if not self.found() and self.required:
-            raise DependencyException('Framework dependency %s not found.' % (name, ))
 
     def get_version(self):
         return 'unknown'

mesonbuild/dependencies/misc.py

@@ -38,7 +38,6 @@ class MPIDependency(ExternalDependency):
     def __init__(self, environment, kwargs):
         language = kwargs.get('language', 'c')
         super().__init__('mpi', environment, language, kwargs)
-        required = kwargs.pop('required', True)
         kwargs['required'] = False
         kwargs['silent'] = True
         self.is_found = False
@@ -108,8 +107,6 @@ class MPIDependency(ExternalDependency):
             mlog.log('Dependency', mlog.bold(self.name), 'for', self.language, 'found:', mlog.green('YES'), self.version)
         else:
             mlog.log('Dependency', mlog.bold(self.name), 'for', self.language, 'found:', mlog.red('NO'))
-            if required:
-                raise DependencyException('MPI dependency {!r} not found'.format(self.name))
 
     def _filter_compile_args(self, args):
         """

mesonbuild/dependencies/ui.py

@@ -227,10 +227,6 @@ class QtBaseDependency(ExternalDependency):
             self.link_args = []
             from_text = '(checked {})'.format(mlog.format_list(methods))
             self.version = 'none'
-            if self.required:
-                err_msg = '{} {} dependency not found {}' \
-                          ''.format(self.qtname, type_text, from_text)
-                raise DependencyException(err_msg)
             if not self.silent:
                 mlog.log(found_msg.format(from_text), mlog.red('NO'))
             return